Twin - Knowledge

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in a decreased twinning propensity in species such as giraffes, elephants, and hippopotami. Despite this adaptation, a case of rare monozygotic twinning has been documented in two elephant calves at the Bandipur Tiger Reserve in Karnataka, India. Chief Veterinarian of the Wildlife Trust of India, NVK Ashraf, in response to the twinning event, wrote that "in species that invest longer time in producing a baby, taking care of two twin calves will be difficult. Therefore, the incidence of twinning will be comparatively less."Ashraf's insight not only illuminates the rarity of twinning among large mammals in the natural world, but directs our attention to the increased twinning propensity of animals under human care. This increased twinning propensity is thought to be either caused by random mutation facilitated by genetic drift, or the positive selection of the "twinning" trait in human-controlled conditions. Due to the removal of natural predators and unpredictable environmental conditions with the increase of human-provided food and medical care, species residing in nature reserves, zoos, etc., carry an increased likelihood of reversing their naturally-selected traits that have been passed on for generations. When considering this phenomenon in relation to twinning, larger mammals not commonly associated with high twinning propensities can perhaps produce twins as an adaptive response to their human-controlled environment. Additionally, the high twinning propensity in species is thought to be positively correlated with the infant mortality rate of the reproducing organism's environment (Rickard, 2022, p.2). Thus if a species lives in a controlled environment with a low infant mortality rate, the frequency of the "twinning trait" could increase, leading to a higher likelihood of producing twin offspring. In the case of the monozygotic twin calves in India, their existence could be connected to a new, positively selected adaptation of twinning attributed to species living under human care (Ward, 2014, p.7-11).

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produce twins because of their small size and insect-based diet (Varella, 2018). This is because their small size indicates shorter gestation periods and the rapid maturation of offspring, resulting in a shorter lifespan where organisms are rapidly replaced by newer generations. The smaller size of the cebidae genus also makes these species more susceptible to predators, thus triggering the heightened pace of birth, maturation, reproduction, and death. Meanwhile, cebidae's insectivorous existence can be correlated with this genus's heightened ability to reproduce, as more resources become available, more organisms can take advantage of these resources. Thus, monkeys that are smaller and have more access to food, such as the cebidae genus, have the ability to produce more offspring at a quicker pace. In terms of dizygotic twinning, it has been observed that older mothers within the cebidae genus have a higher chance of producing twins than those at the beginning stages of their fertility. Despite their access to resources, the cebidae genus has a high mortality rate attributed to their size, meaning that in order to "keep up" their quickened lifecycle, they must produce an excess of offspring in ensuring generational survival. The positively-selected adaptation of twinning counteracts the genus's high mortality rate by giving older mothers the chance to produce more than one offspring. This not only increases the likelihood that one or more of these offspring will reach reproductive maturity, but gives the mother a chance to birth at least one viable offspring despite their age. Due to their short life cycles, the cebidae genus is more inclined to produce dizygotic twins in their older reproductive years, thus signaling that the trait of high twinning propensity is one that is passed down in service of this genus's survival.

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higher twinning propensities. In his study on the evolution of litter size in bats, Garbino discovered that the vespertilionidae genus has higher twinning propensities as a result of their high roosting habitats. When tracked phylogenetically, scientists determined that the common ancestor of bats carried a higher twinning propensity which was then lost, and picked up again, eighteen times in evolutionary history. While other bat subfamilies such as Myotinae and Murinae inevitably lost the twinning trait, the family Vespertilionidae retained a high trait frequency due to mutation and environmental conditions that triggered natural selection. The height and exposed nature of Vespertilionidae's roosting locations resulted in a sharp increase in species mortality rate. Natural selection offsets these dangers by positively selecting high twinning propensity, resulting in not only Vespertilionidae's increased ability to produce twins but the increased likelihood of the genus's reproductive survival. This means that despite the family's high exposure to factors that would seemingly increase mortality rates, Vespertilionidae counteracts their environmental conditions through the evolutionary adaptation of dizygotic twins.

812: 743: 719: 450: 1276:. There is controversy on the best method of delivery where the first twin is head first and the second is not. When the first twin is not head down a caesarean section is often recommended. It is estimated that 75% of twin pregnancies in the United States were delivered by caesarean section in 2008. In comparison, the rate of caesarean section for all pregnancies in the general population varies between 14% and 40%. In twins that share the same placenta, delivery may be considered at 36 weeks. For twins who are born early, there is insufficient evidence for or against placing preterm stable twins in the same cot or incubator (co-bedding). 1599:" (Horton, 2016). Additionally, armadillos have also been known to produce monozygotic twins, sometimes birthing two sets of identical twins during one reproductive cycle. Monozygotic twinning in armadillos functions as an evolutionary adaptation preventing inbreeding. Once an armadillo offspring enters its reproductive stage, the organism is forced to leave the nest in search of its mate, rather than mating with its siblings. Not only does monozygotic twinning dissuade from armadillo siblings inbreeding, but by forcing migration from the nest, this adaptation ensures the increased 1524: 398: 469:, caused by differing environmental influences throughout their lives. Epigenetics refers to the level of activity of any particular gene. A gene may become switched on, switched off, or could become partially switched on or off in an individual. This epigenetic modification is triggered by environmental events. Monozygotic twins can have markedly different epigenetic profiles. A study of 80 pairs of monozygotic twins ranging in age from three to 74 showed that the youngest twins have relatively few 1217: 913:, there were 40 twins and 2 triplets per 1000 births. Twenty-six percent of twins were monozygotic. The incidence of multiple births, which was about five times higher than that observed in any western population, was significantly lower than that of other ethnic groups, who live in the hot and humid climate of the southern part of the country. The incidence of multiple births was related to maternal age but did not bear any association to the climate or prevalence of 217: 1411: 527: 1510:

isolate them from the social environment surrounding them. Idioglossia has been found to be a rare occurrence and the attention of scientists has shifted away from this idea. However, there are researchers and scientists that say cryptophasia or idioglossia is not a rare phenomenon. Current research is looking into the impacts of a richer social environment for these twins to stimulate their development of language.

1069: 718: 42: 742: 80:('non-identical' or 'fraternal'), meaning that each twin develops from a separate egg and each egg is fertilized by its own sperm cell. Since identical twins develop from one zygote, they will share the same sex, while fraternal twins may or may not. In very rare cases twins can have the same mother and different fathers ( 225: 1449:. In their seminal publication, Gabbett, Fisk and colleagues documented a second case of sesquizygosis and presented molecular evidence of the phenomenon. The reported twins shared 100% of their maternal chromosomes and 78% of their paternal genomic information. The authors presented evidence that two 1425:

In 2007, a study reported a case of a pair of living twins, which shared an identical set of maternal chromosomes, while each having a distinct set of paternal chromosomes, albeit from the same man, and thus they most likely share half of their father's genetic makeup. The twins were both found to be

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could be responsible for the high ratio of twins in the area. His theory was rejected by Brazilian scientists who had studied twins living in Linha São Pedro; they suggested genetic factors within that community as a more likely explanation. A high twinning rate has also been observed in other places

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A chimera is an ordinary person or animal except that some of their parts actually came from their twin or from the mother. A chimera may arise either from monozygotic twin fetuses (where it would be impossible to detect), or from dizygotic fetuses, which can be identified by chromosomal comparisons

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Monozygotic twins are genetically nearly identical and they are the same chromosomal sex unless there has been a mutation during development. The children of monozygotic twins test genetically as half-siblings (or full siblings, if a pair of monozygotic twins reproduces with another pair or with the

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Due to the increased parental investment provided for their offspring, larger mammals with longer life spans have slower reproductive cycles and tend to birth only one offspring at a time. This commonly repeated behavior in larger mammals evolved as a fixed, naturally-selected adaptation, resulting

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is defined as a private language that is usually invented by young children, specifically twins. Another term to describe what some people call "twin talk" is cryptophasia where a language is developed by twins that only they can understand. The increased focused communication between two twins may

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Conjoined twins (or the once-commonly used term "siamese") are monozygotic twins whose bodies are joined during pregnancy. This occurs when the zygote starts to split after day 12 following fertilization and fails to separate completely. This condition occurs in about 1 in 50,000 human pregnancies.

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There were 836,104 deliveries of babies in Hesse over the 15-year study period, including 11,740 twin pregnancies, of which only 4,110 met the inclusion criteria and hence were examined in the study. The excluded twin pregnancies were in cases of (1) delivery before 34 weeks of gestation; (2) when

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species, scientists Guilherme Siniciato Terra Garbino (2021) and Marco Varella (2018) have proven that smaller species experiencing infertility in old age and/or unstable habits as a result of increased predation or human interference can experience have undergone natural selection in gaining even

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occurs when a fetus dies after 20 weeks of gestation. There are two types of stillbirth, including intrauterine death and intrapartum death. Intrauterine death occurs when a baby dies during late pregnancy. Intrapartum death, which is more common, occurs when a baby dies while the mother is giving

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known to occur in human populations. Polymorphisms appeared in 2 of the 33 million comparisons, leading the researchers to extrapolate that the blood cells of monozygotic twins may have on the order of one DNA-sequence difference for every 12 million nucleotides, which would imply hundreds of

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The prevalence of dizygotic twinning in monkeys is thought to be an "insurance adaptation" for mothers reproducing at the end of their fertile years. While dizygotic twinning has been observed in species such as gorillas and chimpanzees, monkeys in the cebidae genus are found to be more likely to

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The study stated that the occurrence of complications "was found to be more likely with increasing twin-to-twin delivery time interval" and suggested that the interval be kept short, though it noted that the study did not examine causes of complications and did not control for factors such as the

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The likelihood of a single fertilization resulting in monozygotic twins is uniformly distributed in all populations around the world. This is in marked contrast to dizygotic twinning, which ranges from about six per thousand births in Japan (almost similar to the rate of identical twins, which is

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Jonsson, Hakon; Magnusdottir, Erna; Eggertsson, Hannes P.; Stefansson, Olafur A.; Arnadottir, Gudny A.; Eiriksson, Ogmundur; Zink, Florian; Helgason, Einar A.; Jonsdottir, Ingileif; Gylfason, Arnaldur; Jonasdottir, Adalbjorg; Jonasdottir, Aslaug; Beyter, Doruk; Steingrimsdottir, Thora; Norddahl,

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Among non-twin births, male singletons are slightly (about five percent) more common than female singletons. The rates for singletons vary slightly by country. For example, the sex ratio of birth in the US is 1.05 males/female, while it is 1.07 males/female in Italy. However, males are also more

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Among monozygotic twins, in extremely rare cases, twins have been born with different sexes (one male, one female). When monozygotic twins are born with different sexes it is because of chromosomal defects. The probability of this is so small that multiples having different sexes is universally

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The degree of separation of the twins in utero depends on if and when they split into two zygotes. Dizygotic twins were always two zygotes. Monozygotic twins split into two zygotes at some time very early in the pregnancy. The timing of this separation determines the chorionicity (the number of

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differences. The number of epigenetic differences increases with age. Fifty-year-old twins had over three times the epigenetic difference of three-year-old twins. Twins who had spent their lives apart (such as those adopted by two different sets of parents at birth) had the greatest difference.

163:. There is no known genetic link for identical twinning. Other factors that increase the odds of having fraternal twins include maternal age, fertility drugs and other fertility treatments, nutrition, and prior births. Some women intentionally turn to fertility drugs in order to conceive twins. 1157:

A very rare type of parasitic twinning is one where a single viable twin is endangered when the other zygote becomes cancerous, or "molar". This means that the molar zygote's cellular division continues unchecked, resulting in a cancerous growth that overtakes the viable fetus. Typically, this

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Multiple pregnancies are much less likely to carry to full term than single births, with twin pregnancies lasting on average 37 weeks, three weeks less than full term. Women who have a family history of fraternal twins have a higher chance of producing fraternal twins themselves, as there is a

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Species with small physicalities and quick reproductive cycles carry high twinning propensities as a result of increased predation and high mortality rates. As scientists continue to study the origin of dizygotic twinning in the animal kingdom, many have turned to species that demonstrated an

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differences across the entire genome. The mutations producing the differences detected in this study would have occurred during embryonic cell-division (after the point of fertilization). If they occur early in fetal development, they will be present in a very large proportion of body cells.

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in the animal kingdom are rare but have been recorded on a number of occasions. In 2016, a C-section of an Irish Wolfhound revealed identical twin puppies sharing a singular placenta. South African scientists, who were called in to study the identical twins wrote that... "To the best of our

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There have also been cases in which twins are born a number of days apart. Possibly the worldwide record for the duration of the time gap between the first and the second delivery was the birth of twins 97 days apart in Cologne, Germany, the first of which was born on November 17, 2018.

1488:). If the split occurs later than this time period, the twins risk being conjoined. There is no DNA-based zygosity test that can determine if twins are indeed mirror image. The term "mirror image" is used because the twins, when facing each other, appear as matching reflections. 487:

suggesting that identical twins may not be quite as identical as previously thought. The four-year study of monozygotic (identical) twins and their extended families revealed that these twins have genetic differences that begin in the early stages of embryonic development.

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exams sometimes reveal an "extra" fetus, which fails to develop and instead disintegrates and vanishes in the uterus. There are several reasons for the "vanishing" fetus, including it being embodied or absorbed by the other fetus, placenta or the mother. This is known as

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Mirror image twins result when a fertilized egg splits later in the embryonic stage than normal timing, around day 9–12. This type of twinning could exhibit characteristics with reversed asymmetry, such as opposite dominant handedness, dental structure, or even organs

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in twins compared to single-born children. These studies have converged on the notion that there is a greater rate of delay in language development in twins compared to their single-born counterparts. The reasons for this phenomenon are still in question; however,

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birth. The cause of stillbirth is often unknown, but the rate of babies who are stillborn is higher in twins and multiple births. Caesareans or inductions are advised after 38 weeks of pregnancy for twins, because the risk of stillbirth increases after this time.

542:. Non-conjoined monozygotic twins form up to day 14 of embryonic development, but when twinning occurs after 14 days, the twins will likely be conjoined. Furthermore, there can be various degrees of shared environment of twins in the womb, potentially leading to 4847:

Souter, Vivienne L; Parisi, Melissa A; Nyholt, Dale R; Kapur, Raj P; Henders, Anjali K; Opheim, Kent E; Gunther, Daniel F; Mitchell, Michael E; Glass, Ian A; Montgomery, Grant W (2007). "A case of true hermaphroditism reveals an unusual mechanism of twinning".

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twins can develop differently, due to their genes being differently activated. More unusual are "semi-identical twins", also known as "sesquizygotic". As of 2019, only two cases have been reported. These "half-identical twins" are hypothesized to occur when an

409:. In 18–30% of monozygotic twins each fetus has a separate placenta and a separate amniotic sac. A small number (1–2%) of monozygotic twins share the same placenta and amniotic sac. Fraternal twins each have their own placenta and own amniotic sac. 308:

Dizygotic twins are also more common for older mothers, with twinning rates doubling in mothers over the age of 35. With the advent of technologies and techniques to assist women in getting pregnant, the rate of fraternals has increased markedly.

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Another abnormality that can result in monozygotic twins of different sexes is if the egg is fertilized by a male sperm but during cell division only the X chromosome is duplicated. This results in one normal male (XY) and one female with

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Studies show that there is a genetic proclivity for dizygotic twinning. However, it is only the mother who has any effect on the chances of having such twins; there is no known mechanism for a father to cause the release of more than one

1194:. More than half of twins are born weighing less than 5.5 pounds (2.5 kg), while the average birth weight of a healthy baby should be around 6–8 pounds (3–4 kg). This is largely due to the fact that twins are typically born 1040:

Researchers suspect that as many as 1 in 8 pregnancies start out as multiples, but only a single fetus is brought to full term, because the other fetus has died very early in the pregnancy and has not been detected or recorded. Early

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mothers (who exclude dairy from their diets) are one-fifth as likely to have twins as vegetarian or omnivore mothers, and concluded that "Genotypes favoring elevated IGF and diets including dairy products, especially in areas where

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cycle, identical to the ovulation of dizygotic twins, they produce more than two offspring. Species such as sheep, goats, and deer have a higher propensity for dizygotic twinning, meaning that they carry a higher frequency of the

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Bieber, Frederick R.; Walter E. Nance; Cynthia C. Morton; Judith A. Brown; Fay O. Redwine; Robert L. Jordan and T. Mohanakumar (1981-08-14). "Genetic Studies of an Acardiac Monster: Evidence of Polar Body Twinning in Man".

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The vast majority of twins are either dizygotic (fraternal) or monozygotic (identical). In humans dizygotic twins occur more often than monozygotic twins. Less common variants are discussed further down the article.

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placentae) and amniocity (the number of sacs) of the pregnancy. Dichorionic twins either never divided (i.e.: were dizygotic) or they divided within the first 4 days. Monoamnionic twins divide after the first week.

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Monozygotic twins who share a placenta can develop twin-to-twin transfusion syndrome. This condition means that blood from one twin is being diverted into the other twin. One twin, the 'donor' twin, is small and

2098:"My father is an identical twin and my husband's grandfather is a fraternal twin. Does this increase our changes of having twins, or is the genetic trait only on the mother's side and only for fraternal twins?" 1084:

Most conjoined twins are now evaluated for surgery to attempt to separate them into separate functional bodies. The degree of difficulty rises if a vital organ or structure is shared between twins, such as the

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Am J Med Genet C Semin Med Genet. 2009 May 15;151C(2):136-41. Not really identical: epigenetic differences in monozygotic twins and implications for twin studies in psychiatry. Haque FN, Gottesman II, Wong

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Non-human dizygotic twinning is a common phenomenon in multiple animal species, including cats, dogs, cattle, bats, chimpanzees, and deer. This should not be confused with an animal's ability to produce a

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Twin studies are utilized in an attempt to determine how much of a particular trait is attributable to either genetics or environmental influence. These studies compare monozygotic and dizygotic twins for

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Women undergoing certain fertility treatments may have a greater chance of dizygotic multiple births. In the United States it has been estimated that by 2011 36% of twin births resulted from conception by

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twin. The authors were unable to predict whether a healthy fetus could result from a polar body twinning. However, a study in 2012 found that it is possible for a polar body to result in a healthy fetus.

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Li R, Montpetit A, Rousseau M, Wu SY, Greenwood CM, Spector TD, Pollak M, Polychronakos C, Richards JB (January 2014). "Somatic point mutations occurring early in development: a monozygotic twin study".

1198:. Premature birth and low birth weights, especially when under 3.5 pounds (1.6 kg), can increase the risk of several health-related issues, such as vision and hearing loss, mental disabilities, and 418:

however, because even within the confines of the womb, the fetuses touch different parts of their environment, giving rise to small variations in their corresponding prints and thus making them unique.

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automatically implies dizygotic twins, but if monozygotic twins separate early enough, the arrangement of sacs and placentas in utero is in fact indistinguishable from that of dizygotic twins.

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Unlike singleton gestation where identification of patients at risk for PTL is often difficult, every multiple gestation is at risk for PTL, so all patients can be managed as being at risk.

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influence. Twins that have been separated early in life and raised in separate households are especially sought-after for these studies, which have been used widely in the exploration of

1131:, mystifyingly, was not the mother of two of her three children; she was found to be a chimera, and the two children were conceived from eggs derived from cells of their mother's twin. 1220:

Twin-to-twin transfusion syndrome (TTTS) illustration of twins showing one fetus with exposure to more amniotic fluid while the other is "stuck" with the membrane tightly around itself

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around 4–5) to 15 and more per thousand in some parts of India and up to over 20 in some Central African countries. The exact cause for the splitting of a zygote or embryo is unknown.

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arise from sesquizygotic (semi-identical) twinning which happens when a single egg is fertilized by two sperm and splits the three sets of chromosomes into two separate cell sets.

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Monozygotic twins, although genetically very similar, are not genetically exactly the same. The DNA in white blood cells of 66 pairs of monozygotic twins was analyzed for 506,786

3825: 1940: 1328:. One 1992 study estimates that the frequency of heteropaternal superfecundation among dizygotic twins, whose parents were involved in paternity suits, was approximately 2.4%. 619:(called Monochorionic-Diamniotic "MoDi"), which occurs in 60–70% of the pregnancies with monozygotic twins, and in 0.3% of all pregnancies. Monochorionic-Diamniotic twins are 3740: 4264: 3710: 3267: 504:

showed that although its fetal development suggested that it was an identical twin, as it shared a placenta with its healthy twin, tests revealed that it was probably a

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O. Bomsel-Helmreich; W. Al Mufti (1995). "The mechanism of monozygosity and double ovulation". In Louis G. Keith; Emile Papierik; Donald M. Keith; Barbara Luke (eds.).

155:, the lowest rates are found; only 6 to 9 twin sets per 1,000 live births. North America and Europe have intermediate rates of 9 to 16 twin sets per 1,000 live births. 1375:(45,X). In these cases, although the twins did form from the same fertilized egg, it is incorrect to refer to them as genetically identical, since they have different 2075: 806: 305:. Dizygotic twinning ranges from six per thousand births in Japan (similar to the rate of monozygotic twins) to 14 and more per thousand in some African countries. 127:

have the highest rate of twinning in the world, at 45–50 twin sets (90–100 twins) per 1,000 live births, possibly because of high consumption of a specific type of

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Schmid, O; Trautmann, U; Ashour, H; Ulmer, R; Pfeiffer, RA; Beinder, E (Dec 2000). "Prenatal diagnosis of heterokaryotypic mosaic twins discordant for fetal sex".

3796: 246:(also referred to as "non-identical twins", "dissimilar twins", "biovular twins", and, informally in the case of females, "sororal twins") usually occur when two 4931: 4582: 5200:

Girela, Eloy; Lorente, Jose A.; Alvarez, J. Carlos; Rodrigo, Maria D.; Lorente, Miguel; et al. (1997). "Indisputable double paternity in dizygous twins".

3979: 3037: 1260:. Ectopic pregnancies must be resolved because they can be life-threatening to the mother. However, in most cases, the intrauterine pregnancy can be salvaged. 426:. Normally due to an environmental factor or the deactivation of different X chromosomes in female monozygotic twins, and in some extremely rare cases, due to 5120:

Nieuwint, Aggie; Van Zalen-Sprock, Rieteke; Hummel, Pieter; Pals, Gerard; Van Vugt, John; et al. (1999). "'Identical' twins with discordant karyotypes".

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Various types of chorionicity and amniosity (how the baby's sac looks) in monozygotic (one egg/identical) twins as a result of when the fertilized egg divides

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early in pregnancy, yet the pregnancy will continue; one twin was miscarried but the other was able to be carried to term. This occurrence is similar to the

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from various parts of the body. The number of cells derived from each fetus can vary from one part of the body to another, and often leads to characteristic

847:. In Cândido Godói, one in five pregnancies has resulted in twins. The Argentine historian Jorge Camarasa has put forward the theory that experiments of the 1017:

level of experience of the obstetrician, the wish of the women giving birth, or the "management strategies" of the procedure of delivering the second twin.

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The widespread use of fertility drugs causing hyperovulation (stimulated release of multiple eggs by the mother) has caused what some call an "epidemic of

4114:; (3) when either of the twins had died in the womb before the onset of labor; and (4) when the pregnancy had been complicated by fetal malformations or 4067:

Stein W, Misselwitz B, Schmidt S (2008). "Twin-to-twin delivery time interval: influencing factors and effect on short-term outcome of the second twin".

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towards the other. Sometimes the parasitic twin becomes an almost indistinguishable part of the other, and sometimes this needs to be treated medically.

289:. Dizygotic twins share on average 50 percent of each other's genes, the same as siblings that are conceived and born at different times. Like any other 793:

and procedures such as IVF, which result in multiple births more frequently than unassisted fertilizations do. It may also be linked to the increase of

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From 1980 to 1997, the number of twin births in the United States rose 52%. This rise can at least partly be attributed to the increasing popularity of

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Matte, U; Le Roux, MG; Bénichou, B; Moisan, JP; Giugliani, R (1996). "Study on possible increase in twinning rate at a small village in south Brazil".

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is an exceedingly rare type of dizygotic twinning in which one twin implants in the uterus as normal and the other remains in the fallopian tube as an

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The human twin birth rate in the United States rose 76% from 1980 through 2009, from 9.4 to 16.7 twin sets (18.8 to 33.3 twins) per 1,000 births. The

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Guinness World Record holding twins: https://www.guinnessworldrecords.com/news/2022/11/theyre-so-different-even-though-theyre-identical-twins-725135

3767: 2134: 1886: 297:, particularly as they are the same age. However, dizygotic twins may also look very different from each other (for example, be of opposite sexes). 3847: 3111:

Scott, Richard T.; Treff, Nathan R.; Stevens, John; Forman, Eric J.; Hong, Kathleen H.; Katz-Jaffe, Mandy G.; Schoolcraft, William B. (June 2012).

2580:"Time-lapse recordings reveal why IVF embryos are more likely to develop into twins. Researchers believe the laboratory culture could be the cause" 5502: 1766: 1438:

male. The exact mechanism of fertilization could not be determined but the study stated that it was unlikely to be a case of polar body twinning.

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who happen to develop in the womb together and who are born at the same time, since they arise from two separate eggs fertilized by two separate

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Orwant, Jon. "Heterogeneous learning in the Doppelgänger user modeling system." User Modeling and User-Adapted Interaction 4.2 (1994): 107-130.

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contains two inner cell masses (ICM), each of which will lead to a separate fetus, rather than by the embryo splitting while hatching from the

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and the cell divides into two, with each daughter cell now containing the correct number of chromosomes. The cells continue to develop into a

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Comparison of zygote development in monozygotic and dizygotic twins. In the uterus, a majority of monozygotic twins (60–70%) share the same

4357: 1732: 5116:(Palgrave Macmillan; 2010) 221 pages; explores the experience of child twins, adult twins, and parents of twins, with a focus on Britain. 4996: 3512: 1407:. If the morula then undergoes a twinning event, two embryos will be formed, with different paternal genes but identical maternal genes. 4161:

Gedda, Luigi (1995). "The role of research in twin medicine". In Louis G. Keith; Emile Papiernik; Donald M. Keith; Barbara Luke (eds.).

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is recommended at between 37 and 38 weeks. Vaginal delivery in this case does not worsen the outcome for the infant as compared with

5241:""Masculinizing" effect on respiratory morbidity in girls from unlike-sex preterm twins: a possible transchorionic paracrine effect" 3597: 2156: 1145:

Sometimes one twin fetus will fail to develop completely and continue to cause problems for its surviving twin. One fetus acts as a

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DiDi twins have the lowest mortality risk at about 9 percent, although that is still significantly higher than that of singletons.

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IVF techniques are more likely to create dizygotic twins. For IVF deliveries, there are nearly 21 pairs of twins for every 1,000.

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monozygotic twinning, a 2007 theory related to in vitro fertilization (IVF) proposes that monozygotic twins may be formed when a

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R. Derom; J. Orlebeke; A. Eriksson; M. Thiery (1995). "The epidemiology of multiple births in Europe". In Louis G. Keith (ed.).

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Biswas, A; Su, LL; Mattar, C (Apr 2013). "Caesarean section for preterm birth and, breech presentation and twin pregnancies".

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Female-male twins: This is the most common pairing (50%), encompassing both "female-male" (25%) and "male-female" (25%) twins.

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Martin, Joyce A.; Hamilton, Brady E.; Osterman, Michelle J.K. "Three Decades of Twin Births in the United States, 1980–2009"

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syndrome. Also, in an unknown proportion of cases, two zygotes may fuse soon after fertilization, resulting in a single

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yielded a mean delivery time interval of 13.5 minutes. The delivery interval between the twins was measured as follows:

4451: 5496: 4684: 2579: 2354:

Bortolus, Renata; Fabio Parazzini; Liliane Chatenoud; Guido Benzi; Massimiliano Maria Bianchi; Alberto Marini (1999).

281:

Dizygotic twins, like any other siblings, will practically always have different sequences on each chromosome, due to

5578: 5499:, who are twins and joined the Army on a same day, were promoted to the rank of Major General, again on the same day. 4572: 4115: 4026:

Kulkarni, A. D.; Jamieson, D. J.; Jones, H. W. Jr.; Kissin, D. M.; Gallo, M. F.; MacAluso, M.; Adashi, E. Y. (2013).

3951: 3252: 2900: 1563: 1211: 672: 635: 294: 5240: 4467:"Prospective risk of stillbirth and neonatal complications in twin pregnancies: systematic review and meta-analysis" 3029: 1311:. Classical twin studies are now being supplemented with molecular genetic studies which identify individual genes. 250:

eggs are implanted in the uterus wall at the same time. When two eggs are independently fertilized by two different

5673: 5583: 2275: 958: 1611:

increased output of twins during periods of evolutionary distress and natural selection. Through their studies on

449: 4285: 2828:

Fraga, Mario F.; Ballestar, Esteban; Paz, Maria F.; Ropero, Santiago; Setien, Fernando; et al. (July 2005).

1849: 442: 5527: 2523: 2706:

Machin, GA (January 1996). "Some causes of genotypic and phenotypic discordance in monozygotic twin pairs".

777:

present in dairy products may increase the chance of dizygotic twinning. Specifically, the study found that

4900: 3170:"Postzygotic diploidization of triploids as a source of unusual cases of mosaicism, chimerism and twinning" 1699: 752: 3763: 2126: 1878: 1590:

responsible for the likelihood of twins, rather than the likelihood of litters (Whitcomb, 2021). Cases of

1202:. There is an increased possibility of potential complications as the birth weight of the baby decreases. 366:

Monozygotic twins may also be created artificially by embryo splitting. It can be used as an expansion of

2250: 2215: 931:

Dizygotic twin pregnancies are slightly more likely when the following factors are present in the woman:

17: 4465:

Cheong-See F, Schuit E, Arroyo-Manzano D, Khalil A, Barrett J, Joseph KS, et al. (September 2016).

3949: 3855: 4355: 1762: 786:

is given to cattle, appear to enhance the chances of multiple pregnancies due to ovarian stimulation."

774: 543: 3533: 2538: 5013: 2425: 1166:, resulting in little or no fetus and a cancerous, overgrown placenta, resembling a bunch of grapes. 1042: 748: 701:

Mortality is highest for conjoined twins due to the many complications resulting from shared organs.

5214: 4787: 3423: 3411: 5520: 1534: 1446: 4516:"Co-bedding in neonatal nursery for promoting growth and neurodevelopment in stable preterm twins" 2205: 343:. The chances of having identical twins is relatively rare — around 3 or 4 in every 1,000 births. 5611: 5044: 3885: 3204: 1654: 1538: 458: 382:

Monozygotic twinning occurs in birthing at a rate of about 3 in every 1000 deliveries worldwide.

45:

Identical twins can be difficult to visually distinguish when young, as demonstrated by brothers

3113:"Delivery of a chromosomally normal child from an oocyte with reciprocal aneuploid polar bodies" 1729: 5435: 5209: 4993: 4368: 3509: 3352: 2403: 965: 964:

The risk of twin birth can vary depending on what types of fertility treatments are used. With

367: 35: 5094:

Hayashi, C (2007). "Relationship between Twin Language, Twins' Bond, and Social Competence".

5014:"What are mirror image twins? | Washington State Twin Registry | Washington State University" 4257:"Very Low Birthweight - Online Medical Encyclopedia - University of Rochester Medical Center" 2537:

Oleszczuk, Jaroslaw J.; Donald M. Keith; Louis G. Keith; William F. Rayburn (November 1999).

2305: 1253: 683:

Monoamniotic twins occur when the split takes place after the ninth day after fertilization.

474:

However, certain characteristics become more alike as twins age, such as IQ and personality.

282: 46: 31: 3344: 5439: 5406: 5299: 4227: 3069: 2841: 2426:"Study: Time-lapse recordings reveal why IVF embryos are more likely to develop into twins" 1983: 1591: 1497: 1072: 790: 435: 2240: 992:

A 15-year German study of 8,220 vaginally delivered twins (that is, 4,110 pregnancies) in

732:

with the head pointing towards upper left. The twin at right in the image is shown in the

8: 5570: 3570: 1419: 1304: 604: 5303: 4659: 3253:"Semi-identical twins are rare, and doctors say they've identified the second case ever" 3073: 2977:

Gudmundur L. (2021-01-07). "Differences between germline genomes of monozygotic twins".

2845: 2536: 1987: 5642: 5588: 5398: 5386: 5322: 5287: 5268: 5188: 5145: 4873: 4629: 4604: 4548: 4515: 4491: 4466: 4419: 4394: 4166: 4092: 3950:

Fernand Leroy; Taiwo Olaleye-Oruene; Gesina Koeppen-Schomerus; Elizabeth Bryan (2002).

3932: 3920: 3691: 3300: 3220: 3145: 3112: 3085: 3010: 2864: 2829: 2810: 2766: 2683: 2658: 2634: 2609: 2245: 2210: 2006: 1971: 1704: 1649: 1595:

knowledge, this is the first report of monozygotic twinning in the dog confirmed using

1462: 1442: 1427: 1343: 1163: 1109: 1051: 844: 647: 5223: 3382: 3288: 5390: 5354: 5344: 5327: 5260: 5227: 5180: 5137: 5061: 5057: 4976: 4865: 4769: 4702: 4692: 4634: 4553: 4535: 4496: 4424: 4338: 4174: 4111: 4084: 4049: 3971: 3924: 3683: 3648: 3640: 3630: 3589: 3545: 3534:"Mechanisms of twinning: VII. Effect of diet and heredity on the human twinning rate" 3470: 3427: 3356: 3345: 3304: 3292: 3191: 3150: 3132: 3093: 3058: 3014: 3002: 2994: 2939: 2929: 2906: 2896: 2889: 2869: 2802: 2758: 2723: 2688: 2639: 2550: 2517: 2479: 2474: 2457: 2385: 2377: 2331: 2187: 2046: 2011: 1967: 1912: 1882: 1600: 1415: 1273: 1257: 843:

to 10% for Linha São Pedro, a tiny Brazilian settlement which belongs to the city of

513: 497: 5272: 5192: 5149: 4096: 3936: 3695: 3224: 2770: 1796: 595:

Dichorionic-Diamniotic twins form when splitting takes place by the third day after

5683: 5678: 5462: 5402: 5382: 5317: 5307: 5252: 5219: 5170: 5129: 5053: 4966: 4877: 4857: 4759: 4749: 4624: 4616: 4543: 4531: 4527: 4486: 4478: 4414: 4406: 4367:. Royal College of Obstetricians and Gynaecologist. pp. 70–103. Archived from 4330: 4076: 4039: 3963: 3916: 3675: 3490: 3460: 3284: 3212: 3181: 3140: 3124: 3077: 2986: 2859: 2849: 2814: 2794: 2750: 2715: 2678: 2670: 2629: 2621: 2469: 2367: 2353: 2179: 2038: 2001: 1991: 1689: 1612: 1578: 1350:, which exhibit differing ethnic and racial features. One such pairing was born in 1325: 1269: 1195: 968:(IVF), this is primarily due to the insertion of multiple embryos into the uterus. 879: 574: 81: 4334: 2798: 2625: 5598: 5000: 4410: 4356:

National Collaborating Centre for Women's and Children's Health (November 2011).

4170: 3747: 3516: 3497: 3407: 2957:

Mandler, G (2001). "Apart from genetics: What makes monozygotic twins similar?".

2097: 1996: 1802: 1736: 1664: 1372: 1268:

For otherwise healthy twin pregnancies where both twins are head down a trial of

1128: 1063: 706: 688: 539: 483: 371: 198:

is higher for twins, it leads to female twins being more common than male twins.

128: 5239:

Shinwell ES, Reichman B, Lerner-Geva L, Boyko V, Blickstein I (September 2007).

4924:"Doctors say they have identified rare set of semi-identical twins in Australia" 2170:

Nylander, Percy P. S. (July 1981). "The Factors That Influence Twinning Rates".

2029:

Elliott, JP (December 2008). "Preterm labor in twins and high-order multiples".

1639: 1465:

lethality, while the other two cell lines, each consisting of the same maternal

397: 182:

Male–male twins: Sometimes called fraternal (unrelated to zygosity) twins (25%).

112: 5637: 5606: 5292:

Proceedings of the National Academy of Sciences of the United States of America

4514:

Lai, Nai Ming; Foong, Siew Cheng; Foong, Wai Cheng; Tan, Kenneth (2016-04-14).

2990: 1679: 1545: 1485: 1199: 1179: 1140: 1047: 1035: 891: 794: 783: 760: 729: 676: 501: 360: 152: 140: 100: 5479:"Twin Zygosity Test for Dichorionic Diamniotic (Di/Di) Twins! Zygosity Reveal" 5175: 5158: 4971: 4954: 4861: 4818: 4395:"Trends in caesarean delivery for twin births in the United States: 1995-2008" 4080: 3679: 3128: 2183: 2042: 1817: 1216: 414:

same person), rather than first cousins. Identical twins do not have the same

5668: 5662: 5616: 5358: 4706: 4539: 4443: 3750: 3644: 3136: 2998: 2381: 2372: 2355: 1659: 1596: 1581:, because while litters are caused by the release of multiple eggs during an 1458: 1400: 940: 895: 883: 852: 840: 831:

About 1 in 90 human births (1.1%) results from a twin pregnancy. The rate of

824: 756: 733: 725: 698:

into 2 embryos occurs, 99% of the time it is within 8 days of fertilization.

596: 247: 144: 132: 124: 5312: 3652: 3449:"Monochorionic diamniotic infants without twin-to-twin transfusion syndrome" 3186: 3169: 3081: 2943: 2910: 2854: 5394: 5331: 5264: 5256: 5141: 5065: 4869: 4773: 4710: 4577: 4557: 4500: 4428: 4342: 4088: 4053: 3975: 3593: 3549: 3474: 3419: 3296: 3195: 3154: 3006: 2873: 2806: 2762: 2720:

10.1002/(SICI)1096-8628(19960122)61:3<216::AID-AJMG5>3.0.CO;2-S

2643: 2587: 2554: 2483: 2389: 2050: 2015: 1709: 1502: 1435: 1308: 1230: 1191: 906: 671:

Monoamniotic twins, as with diamniotic monochorionic twins, have a risk of

668:

The survival rate for monoamniotic twins is somewhere between 50% and 60%.

616: 582: 406: 251: 5231: 5184: 4980: 4754: 4737: 4044: 4027: 3967: 3928: 3789:"Seeing double: the village in deepest Kerala where twins have taken over" 3687: 3465: 3448: 3097: 2727: 2692: 2456:

Illmensee K, Levanduski M, Vidali A, Husami N, Goudas VT (February 2009).

2191: 224: 5647: 4738:"Molecular Support for Heterogonesis Resulting in Sesquizygotic Twinning" 4638: 3216: 2430: 1674: 1506: 1441:

The likely genetic basis of semi-identical twins was reported in 2019 by

1387: 1347: 1337: 1175: 973: 936: 898:, the twinning rate exceeded 3% of all births. Nevertheless, the rate of 662: 586: 470: 466: 415: 5134:

10.1002/(SICI)1097-0223(199901)19:1<72::AID-PD465>3.0.CO;2-V

4764: 4620: 2674: 1805:, National Center for Health Statistics Data Brief, No. 80, January 2012 1461:

to form three cell lines. The purely paternal cell line died out due to

1303:

characteristics to try to isolate genetic influence from epigenetic and

984:) has a relatively less but yet significant risk of multiple pregnancy. 4603:

Schmidt, R; EH Sobel; HM Nitowsky; H Dar; FH Allen Jr (February 1976).

3275: 3089: 2975: 2830:"Epigenetic differences arise during the lifetime of monozygotic twins" 2325: 1694: 1684: 1669: 1300: 1285: 1241: 624: 505: 454: 427: 356: 148: 143:, there are 18–30 twin sets (or 36–60 twins) per 1,000 live births. In 108: 4482: 3907:

Rehan N, Tafida DS (November 1980). "Multiple births in Hausa women".

3030:"Identical twins aren't always genetically identical, new study finds" 2539:"Projections of population-based twinning rates through the year 2100" 1068: 216: 1644: 1582: 1376: 1182:

syndrome, but typically occurs later, as the twin is not reabsorbed.

1159: 1116: 977: 836: 755:

of 15 weeks. There is no sign of any membrane between the fetuses. A

431: 278:, just like ordinary siblings. This is the most common type of twin. 160: 61: 57: 5368:"Selection for Increased Brood Size in Historical Human Populations" 4464: 2755:

10.1002/1097-0223(200012)20:12<999::aid-pd948>3.0.co;2-e

1123:, composed of cells from a male twin and a female twin. In one case 763:

of parts of the upper thorax and head is shown of the twin at right.

5552: 4393:

Lee HC, Gould JB, Boscardin WJ, El-Sayed YY, Blumenfeld YJ (2011).

4323:

Best Practice & Research. Clinical Obstetrics & Gynaecology

4163:

Multiple Pregnancy: Epidemiology, Gestation & Perinatal Outcome

2328:

Multiple Pregnancy: Epidemiology, Gestation & Perinatal Outcome

2157:"Chinese Women Try to Bypass One-Child Policy With Pills for Twins" 1909:

Multiple Pregnancy: Epidemiology, Gestation & Perinatal Outcome

1431: 1296: 1146: 1124: 1120: 1076: 860: 778: 631: 610: 550: 423: 402: 201: 5512: 5459:"Facts About Multiples: An Encyclopedia of Multiple Birth Records" 5119: 2458:"Human embryo twinning with applications in reproductive medicine" 1814: 4927: 3626: 3446: 1634: 1616: 1410: 1292: 914: 910: 869: 864: 819:

twin figures (early 20th-century) in the permanent collection of

705:

If the division of the zygote occurs later than the 12 days then

578: 478: 290: 286: 271: 5238: 2891:

Entwined lives: twins and what they tell us about human behavior

972:

without IVF has a very high risk of multiple birth. Reversal of

5042:

Thorpe, K (June 2006). "Twin children's language development".

4602: 4131:"I'll do it my way: twin is born three months after her sister" 4028:"Fertility Treatments and Multiple Births in the United States" 3447:

Cordero L, Franco A, Joy SD, O'Shaughnessy RW (December 2005).

2455: 2302:"Identical and Fraternal Twins – Determining Zygosity in Twins" 1587: 1470: 1404: 1367:

clinical determination that the multiples are not monozygotic.

1351: 1226: 873: 695: 653: 526: 340: 336: 259: 205: 92: 73: 69: 3711:"Nazi Angel of death Josef Mengel created twin town in Brazil" 3519:

By Pamela Prindle Fierro, About.com. Retrieved on July 9, 2009

1906: 1815:

Zach, Terence; Arun K Pramanik; Susannah P Ford (2007-10-02).

928:

The predisposing factors of monozygotic twinning are unknown.

728:

as part of IVF. The twin at left in the image is shown in the

41: 5365: 5341:

Identical Strangers: A Memoir of Twins Separated and Reunited

1823: 1450: 1396: 1097: 1093: 1089: 1085: 993: 839:, ranging as high as about 45 per 1000 births (4.5%) for the 816: 275: 136: 111:

whose resemblance parallels that of twins are referred to as

88: 2406:. MedlinePlus, US National Library of Medicine. 11 July 2022 2404:"Is the probability of having twins determined by genetics?" 1603:

and geographical population diffusion of armadillo species.

1457:

simultaneously. The chromosomes assorted themselves through

1233:. The lives of both twins are endangered by this condition. 477:

In January 2021, new research from a team of researchers in

339:(hence, "monozygotic") which then divides into two separate 5199: 4025: 1454: 1392: 848: 363:(the gelatinous protective coating around the blastocyst). 332: 302: 3665: 3414:. In Robert Resnik; Robert K. Creasy; Jay D. Iams (eds.). 2740: 1933:"What's in a yam? Clues to fertility, a student discovers" 461:

have become distinguishable from each other by adulthood.

179:

Female–female twins: Sometimes called sororal twins (25%).

4788:"Rare new kind of twins: boy and girl are semi-identical" 4392: 1466: 807:

Populated places with highest incidence of multiple birth

724:

Dichorionic-diamniotic twins at 8 weeks and 5 days since

465:

Another cause of difference between monozygotic twins is

5288:"Male twins reduce fitness of female co-twins in humans" 5156: 4846: 3741:

Nazi 'Angel of Death' not responsible for town of twins

3110: 2827: 1382: 1357: 1079:) in 1811, were the origin of the term "Siamese twins". 4066: 2172:

Acta Geneticae Medicae et Gemellologiae: Twin Research

1965: 827:

have the highest dizygotic twinning rate in the world.

491: 370:(IVF) to increase the number of available embryos for 5338: 4748:(9). Boston: Massachusetts Medical Society: 842–849. 4736:

Gabbett, Michael T.; et al. (28 February 2019).

3568: 2783: 2584:

European Society of Human Reproduction and Embryology

4893:"Study describes new type of "semi-identical" twins" 1205: 1119:

skin coloration in human chimeras. A chimera may be

920:

Twins are more common in people of African descent.

392: 5495:Twin brothers promoted as Majors General together. 5285: 27:

One of two offspring produced by the same pregnancy

5366:Helle, Samuli; Virpi Lummaa; Jukka Jokela (2004). 5159:"How frequent is heteropaternal superfecundation?" 5114:Twins in Society: Parents, Bodies, Space, and Talk 4953:Gedda L, Sciacca A, Brenci G, et al. (1984). 4952: 4195: 4129: 2888: 1816: 902:twins remains at about 1 in 333 across the globe. 95:(the much more common case in humans) is called a 68:('identical'), meaning that they develop from one 5003:. Proactivegenetics.com. Retrieved on 2013-08-10. 3486: 3484: 2304:. Multiples.about.com. 2013-07-16. Archived from 1752:in "Human Heredity Principles and issues" p. 104. 1024: 270:. Fraternal twins are, essentially, two ordinary 5660: 5157:Wenk RE, Houtz T, Brooks M, Chiafari FA (1992). 4994:Twins genetics, details of environmental impacts 4955:"Situs viscerum specularis in monozygotic twins" 4513: 3952:"Yoruba Customs and Beliefs Pertaining to Twins" 3878:"Mohammadpur Umri, THE VILLAGE OF TWINS !!" 3416:Maternal-Fetal Medicine: Principles and Practice 3351:. Washington, DC: Taylor & Francis. p. 2278:. Washington State Twin Registry. October 2015. 1354:in 1993 to a white mother and Caribbean father. 1229:, the other, the 'recipient' twin, is large and 1190:It is very common for twins to be born at a low 312: 4441: 3569:Martin, Joyce A; Melissa M. Park (1999-09-14). 3342: 2656: 1763:"Twins, Triplets, Multiple Births: MedlinePlus" 573:Normally, twins have two separate (di- being a 4320: 4286:"Pregnant with twins: potential complications" 3620: 3481: 3202: 3027: 1496:There have been many studies highlighting the 1469:but only 50% identical paternal DNA, formed a 211: 99:, and the general term for one offspring of a 5528: 5286:Lummaa V, Pettay JE, Russell AF (June 2007). 3376: 3374: 3372: 3117:Journal of Assisted Reproduction and Genetics 2490: 949:She is greater than average height and weight 623:monozygotic, with a few exceptions where the 175:Fraternal twins can be any of the following: 4458: 4386: 4349: 3571:"Trends in Twin and Triplet Births: 1980–97" 3510:MoMo Twins; Monochorionic Monoamniotic Twins 2777: 2610:"Mechanical control of tissue morphogenesis" 2276:"Are there more male twins or female twins?" 905:In a study on the maternity records of 5750 5079:Usher, L (13 October 2000). "Idioglossia". 4520:The Cochrane Database of Systematic Reviews 3906: 3884:. Business Directory Plugin. Archived from 3623:Progress in Reproductive Medicine Volume II 2349: 2347: 1324:This phenomenon is known as heteropaternal 894:". In 2001, for the first time ever in the 512:In 2003, a study argued that many cases of 453:Despite being genetically identical, twins 254:, fraternal twins result. The two eggs, or 5535: 5521: 4816: 4316: 4314: 4312: 4310: 3708: 3406: 3369: 3338: 3336: 3334: 3332: 3330: 3328: 3167: 2734: 2607: 2505:. Archived from the original on 2001-05-27 1723: 5321: 5311: 5213: 5174: 4970: 4763: 4753: 4628: 4547: 4490: 4418: 4193: 4127: 4043: 3491:Pregnancy-Info -- > Monoamniotic Twins 3464: 3185: 3144: 2863: 2853: 2682: 2633: 2473: 2371: 2068:"Probability of having twins hereditary?" 2005: 1995: 1564:Learn how and when to remove this message 1548:so that sources are clearly identifiable. 952:She has had several previous pregnancies. 946:She is between the age of 30 and 40 years 656:in 1–2% of monozygotic twin pregnancies. 4691:. Sunderland, Mass: Sinauer Associates. 4570: 4007:. University of Rochester Medical Center 3531: 3527: 3525: 2657:Edwards JH, Dent T, Kahn J (June 1966). 2496: 2344: 2169: 1961: 1959: 1957: 1850:"Genetics or yams in the Land of Twins?" 1409: 1248: 1215: 1067: 810: 525: 448: 396: 223: 215: 40: 5339:Schein, Elyse; Paula Bernstein (2007). 5163:Acta Geneticae Medicae et Gemellologiae 5093: 4899:. Thomson Reuters Trust. Archived from 4884: 4735: 4731: 4729: 4727: 4682: 4307: 4154: 3440: 3325: 2956: 2028: 1491: 923: 615:Monochorionic twins generally have two 519: 422:Monozygotic twins always have the same 228:Fraternal twin brothers as young babies 14: 5661: 5041: 4921: 4890: 4605:"Monozygotic twins discordant for sex" 3380: 2923: 2895:. New York: Dutton. pp. 135–138. 2705: 2133:. Associated Press. 14 February 2006. 1972:"Twinning across the Developing World" 1399:. The cell assorts the chromosomes by 1263: 1152: 549:It is a common misconception that two 5516: 5078: 4798:from the original on 28 February 2019 4794:. Thomson Reuters. 28 February 2019. 4194:Ainsworth, Chris (15 November 2003). 4160: 3900: 3621:Asch, Richard H.; John Studd (1995). 3586:National Center for Health Statistics 3522: 3503: 2886: 2356:"The epidemiology of multiple births" 2294: 2095: 1954: 1478: 1473:which subsequently split into twins. 1279: 909:women living in the Savannah zone of 821:The Children's Museum of Indianapolis 430:, twins may express different sexual 166: 159:genetically linked tendency to hyper- 139:to release an egg from each side. In 4724: 4442:James Gallagher (23 November 2011). 4060: 3614: 3265: 3231:from the original on 29 October 2021 3040:from the original on 11 January 2021 2708:American Journal of Medical Genetics 2659:"Monozygotic twins of different sex" 2543:The Journal of Reproductive Medicine 2268: 2137:from the original on 6 December 2008 1970:(2011). Newell, Marie-Louise (ed.). 1517: 1383:Semi-identical (sesquizygotic) twins 1358:Monozygotic twins of different sexes 1319: 1314: 1174:Occasionally, a woman will suffer a 987: 759:is shown of the twin at left, and a 694:When the division of the developing 5542: 4142:from the original on 30 August 2021 3828:from the original on 29 August 2018 3422:: W. B. Saunders Company. pp. 3205:"'Semi-identical' twins discovered" 2396: 2330:. Taylor and Francis. p. 145. 2127:"China: Drug bid to beat child ban" 1750:5-7 Twin Studies and Complex Traits 1739:Last Editorial Review: 19 June 2000 1730:MedicineNet > Definition of Twin 1505:was thought to be the major cause. 1185: 652:Monochorionic twins share the same 630:Monochorionic twins share the same 609:Monochorionic twins share the same 492:Polar body and semi-identical twins 24: 5476: 5456: 5387:10.1111/j.0014-3820.2004.tb01658.x 5106: 4922:Molina, Brett (28 February 2019). 4444:"Women can choose Caesarean birth" 4128:Crossland, David (16 April 2019). 3921:10.1111/j.1471-0528.1980.tb04464.x 3824:. Bennett, Coleman & Co. Ltd. 3168:Golubovsky, M.D. (February 2003). 1911:. Taylor and Francis. p. 34. 1169: 1134: 1057: 1029: 736:with the head pointing rightwards. 25: 5695: 5579:Twin-to-twin transfusion syndrome 5508: 4685:"Non-identical Monozygotic Twins" 4208:from the original on 20 June 2015 4116:Twin-to-twin transfusion syndrome 3578:National Vital Statistics Reports 2282:from the original on 24 July 2018 1212:Twin-to-twin transfusion syndrome 1206:Twin-to-twin transfusion syndrome 1158:results when one twin has either 673:twin-to-twin transfusion syndrome 636:twin-to-twin transfusion syndrome 538:In very rare cases, twins become 393:Genetic and epigenetic similarity 204:is the degree of identity in the 5584:Twin reversed arterial perfusion 5096:Twin Research and Human Genetics 5058:10.1016/j.earlhumdev.2006.03.012 4454:from the original on 2012-08-19. 4110:the first twin was delivered by 4001:"Overview of Multiple Pregnancy" 3721:from the original on 19 May 2019 3385:. Focus Information Technology. 3343:Shulman LS, van Vugt JG (2006). 3203:John Whitfield (26 March 2007). 2608:Patwari P, Lee RT (2008-08-01). 2475:10.1016/j.fertnstert.2008.12.098 2096:Fitch, Karen (26 January 2005). 1546:add missing citation information 1522: 1453:from the same man fertilized an 959:assisted reproductive technology 741: 717: 190:susceptible than females to die 5425:"TWINS Guide to the First Year" 5087: 5072: 5035: 5024:from the original on 2018-09-05 5006: 4987: 4946: 4915: 4840: 4829:from the original on 2023-04-29 4810: 4780: 4742:New England Journal of Medicine 4676: 4645: 4596: 4585:from the original on 2018-01-19 4571:Moorhead, Joanna (2011-09-24). 4564: 4507: 4435: 4296:from the original on 2015-11-09 4278: 4267:from the original on 2018-01-19 4249: 4238:from the original on 2019-04-05 4228:"Risks Linked With Twin Births" 4220: 4187: 4121: 4103: 4032:New England Journal of Medicine 4019: 3993: 3989:– via Randafricanart.com. 3982:from the original on 2017-09-02 3943: 3870: 3840: 3810: 3781: 3770:from the original on 2009-07-18 3766:. BBC World News. 7 June 2001. 3756: 3733: 3702: 3659: 3603:from the original on 2017-11-13 3562: 3400: 3389:from the original on 2008-06-16 3259: 3245: 3161: 3104: 3052: 3021: 2969: 2950: 2917: 2880: 2821: 2699: 2650: 2601: 2572: 2561:from the original on 2009-01-04 2530: 2449: 2438:from the original on 2019-08-05 2418: 2319: 2257:from the original on 2021-07-01 2233: 2222:from the original on 2021-12-12 2198: 2163: 2149: 2119: 2108:from the original on 2022-06-24 2089: 2078:from the original on 2022-09-25 2060: 2022: 1943:from the original on 2022-05-07 1925: 1889:from the original on 2008-12-15 1860:from the original on 2017-02-23 1831:from the original on 2008-09-25 1769:from the original on 2016-06-03 768: 443:single-nucleotide polymorphisms 82:heteropaternal superfecundation 5018:Washington State Twin Registry 4959:Acta Genet Med Gemellol (Roma) 4891:Dunham, Will (26 March 2007). 4532:10.1002/14651858.CD008313.pub3 3854:. 4Skylark.com. Archived from 3709:Nick Evans (21 January 2009). 3668:Acta Genet Med Gemellol (Roma) 2497:Holladay, April (2001-05-09). 1900: 1871: 1842: 1808: 1789: 1780: 1755: 1742: 1363:accepted as a sound basis for 1331: 1236: 1025:Complications during pregnancy 835:twinning varies greatly among 13: 1: 5224:10.1016/S0015-0282(97)81456-2 4335:10.1016/j.bpobgyn.2012.09.002 3795:. 12 May 2009. Archived from 3289:10.1016/s0140-6736(03)14237-7 3028:Lianne Kolirin (8 Jan 2021). 2799:10.1136/jmedgenet-2013-101712 2626:10.1161/CIRCRESAHA.108.175331 1716: 481:was published in the journal 313:Monozygotic (identical) twins 118: 72:, which splits and forms two 4411:10.1097/AOG.0b013e3182318651 2959:Journal of Mind and Behavior 2834:Proc. Natl. Acad. Sci. U.S.A 2586:. 2007-07-02. Archived from 1997:10.1371/journal.pone.0025239 1700:Twin towns and sister cities 1103: 800: 773:A 2006 study has found that 377: 346: 7: 4930:. USA TODAY. Archived from 4817:NEJM Group (4 March 2019). 4609:Journal of Medical Genetics 3848:"Twin Capital Of The World" 3532:Steinman, Gary (May 2006). 3381:Curran, Mark (2005-11-02). 2663:Journal of Medical Genetics 2251:Central Intelligence Agency 2216:Central Intelligence Agency 2159:. ABC News. August 3, 2011. 1627: 1054:embryo, and, later, fetus. 751:of monoamniotic twins at a 496:A 1981 study of a deceased 438:zygote splitting unevenly. 212:Dizygotic (fraternal) twins 194:, and since the death rate 91:that develops alone in the 10: 5700: 5343:. New York: Random House. 4683:Gilbert, Scott F. (2006). 2991:10.1038/s41588-020-00755-1 1513: 1335: 1283: 1209: 1138: 1107: 1061: 1033: 804: 775:insulin-like growth factor 648:Monochorionic-Monoamniotic 634:, and thus have a risk of 335:is fertilized to form one 29: 5630: 5597: 5569: 5551: 5176:10.1017/S000156600000249X 5081:Times Literary Supplement 4972:10.1017/S0001566000007546 4862:10.1007/s00439-006-0279-x 4081:10.1080/00016340801934276 4069:Acta Obstet Gynecol Scand 3680:10.1017/S0001566000000829 3500:Retrieved on July 9, 2009 3129:10.1007/s10815-012-9746-6 2522:: CS1 maint: unfit URL ( 2499:"What triggers twinning?" 2360:Human Reproduction Update 2184:10.1017/s0001566000007650 2043:10.1016/j.clp.2007.10.004 1346:couples can sometimes be 1127:determined that a woman, 1043:obstetric ultrasonography 856:of the world, including: 749:Abdominal ultrasonography 351:Regarding spontaneous or 4819:"Sesquizygotic Twinning" 2928:. New York: Worth Pubs. 2887:Segal, Nancy L. (1999). 2104:. The Tech Interactive. 1000:Within 15 minutes: 75.8% 970:Ovarian hyperstimulation 709:are usually the result. 605:Monochorionic-Diamniotic 135:which may stimulate the 5674:Reproduction in mammals 5612:Craniopagus parasiticus 5313:10.1073/pnas.0605875104 5202:Fertility and Sterility 5045:Early Human Development 4573:"Black and white twins" 3753:online, 27 January 2009 3082:10.1126/science.7196086 2924:Plomin, Robert (2001). 2855:10.1073/pnas.0500398102 2206:"United States: People" 2074:. Columbia University. 2031:Clinics in Perinatology 1655:List of multiple births 1498:development of language 980:(trade names including 679:due to lack of oxygen. 658:Monoamniotic twins are 570:Dichorionic-Diamniotic 544:pregnancy complications 467:epigenetic modification 434:, normally from an XXY 5438:. 2008. Archived from 5436:Fort Collins, Colorado 5257:10.1542/peds.2006-3574 4261:www.urmc.rochester.edu 2373:10.1093/humupd/5.2.179 1937:Yale Medicine Magazine 1422: 1221: 1080: 966:in vitro fertilisation 828: 531: 462: 410: 368:in vitro fertilization 229: 221: 64:. Twins can be either 50: 36:Twins (disambiguation) 4755:10.1056/NEJMoa1701313 4689:Developmental biology 4653:"The Zygosity Puzzle" 4197:"The stranger within" 4045:10.1056/NEJMoa1301467 3968:10.1375/1369052023009 3466:10.1038/sj.jp.7211405 3187:10.1093/humrep/deg060 1748:Michael R. Cummings, 1660:List of notable twins 1413: 1395:is fertilized by two 1342:Dizygotic twins from 1254:Heterotopic pregnancy 1249:Heterotopic pregnancy 1219: 1162:or complete paternal 1071: 1012:Over 60 minutes: 1.8% 814: 529: 452: 400: 283:chromosomal crossover 227: 220:Adult fraternal twins 219: 131:containing a natural 60:produced by the same 47:Billy and Bobby Mauch 44: 32:Twin (disambiguation) 5497:Seneviratne brothers 3909:Br J Obstet Gynaecol 3818:"A village of twins" 3412:"Multiple Gestation" 3217:10.1038/news070326-1 2614:Circulation Research 1592:monozygotic twinning 1533:needs more complete 1492:Language development 1075:, born in Siam (now 1073:Chang and Eng Bunker 1003:16–30 minutes: 16.4% 939:descent (especially 924:Predisposing factors 520:Degree of separation 436:Klinefelter syndrome 331:occur when a single 30:For other uses, see 5571:Monochorionic twins 5304:2007PNAS..10410915L 4934:on 28 February 2019 4903:on 28 February 2019 4621:10.1136/jmg.13.1.64 4358:"Caesarean section" 4005:Health Encyclopedia 3764:"The Land Of Twins" 3074:1981Sci...213..775B 2926:Behavioral genetics 2846:2005PNAS..10210604F 2675:10.1136/jmg.3.2.117 1988:2011PLoSO...625239S 1879:"The Land of Twins" 1420:Miles City, Montana 1414:Twin calves of the 1264:Management of birth 1153:Partial molar twins 1009:46–60 minutes: 1.7% 1006:31–45 minutes: 4.3% 589:(identical) twins. 5589:Monoamniotic twins 5457:Samson, Jennifer. 5122:Prenatal Diagnosis 4999:2021-08-31 at the 4167:Taylor and Francis 3746:2014-10-25 at the 3515:2016-04-08 at the 3496:2019-11-03 at the 3174:Human Reproduction 2246:The World Factbook 2211:The World Factbook 1854:Independent Online 1801:2017-12-18 at the 1735:2013-10-22 at the 1705:Twins in mythology 1650:Gemini (astrology) 1479:Mirror image twins 1463:genomic imprinting 1423: 1280:Human twin studies 1222: 1164:uniparental disomy 1110:Chimera (genetics) 1081: 829: 532: 463: 411: 405:but have separate 293:, dizygotic twins 262:, hence the terms 230: 222: 167:Types and zygosity 51: 5656: 5655: 5350:978-1-4000-6496-0 4698:978-0-87893-250-4 4483:10.1136/bmj.i4353 4180:978-1-85070-666-3 4112:caesarean section 4038:(23): 2218–2225. 3858:on 4 October 2015 3636:978-1-85070-574-1 3433:978-0-7216-0004-8 3362:978-0-8247-2844-1 3347:Prenatal medicine 3068:(4509): 775–777. 2935:978-0-7167-5159-5 2582:(Press release). 2337:978-1-85070-666-3 1968:Christiaan Monden 1918:978-1-85070-666-3 1883:BBC World Service 1818:"Multiple Births" 1601:genetic variation 1574: 1573: 1566: 1320:Bi-paternal twins 1315:Unusual twinnings 1274:Caesarean section 1258:ectopic pregnancy 988:Delivery interval 815:A pair of female 713: 712: 16:(Redirected from 5691: 5537: 5530: 5523: 5514: 5513: 5488: 5486: 5485: 5473: 5471: 5470: 5461:. 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Archived from 3283:(9385): 735–43. 3272: 3266:Hall JG (2003). 3263: 3257: 3256: 3249: 3243: 3240: 3238: 3236: 3199: 3189: 3165: 3159: 3158: 3148: 3108: 3102: 3101: 3056: 3050: 3049: 3047: 3045: 3025: 3019: 3018: 2973: 2967: 2966: 2954: 2948: 2947: 2921: 2915: 2914: 2894: 2884: 2878: 2877: 2867: 2857: 2825: 2819: 2818: 2781: 2775: 2774: 2749:(12): 999–1003. 2738: 2732: 2731: 2703: 2697: 2696: 2686: 2654: 2648: 2647: 2637: 2605: 2599: 2598: 2596: 2595: 2576: 2570: 2569: 2567: 2566: 2534: 2528: 2527: 2521: 2513: 2511: 2510: 2494: 2488: 2487: 2477: 2453: 2447: 2446: 2444: 2443: 2422: 2416: 2415: 2413: 2411: 2400: 2394: 2393: 2375: 2351: 2342: 2341: 2323: 2317: 2316: 2314: 2313: 2298: 2292: 2291: 2289: 2287: 2272: 2266: 2265: 2263: 2262: 2237: 2231: 2230: 2228: 2227: 2202: 2196: 2195: 2167: 2161: 2160: 2153: 2147: 2146: 2144: 2142: 2123: 2117: 2116: 2114: 2113: 2102:Ask a Geneticist 2093: 2087: 2086: 2084: 2083: 2064: 2058: 2057: 2026: 2020: 2019: 2009: 1999: 1963: 1952: 1951: 1949: 1948: 1929: 1923: 1922: 1904: 1898: 1897: 1895: 1894: 1875: 1869: 1868: 1866: 1865: 1846: 1840: 1839: 1837: 1836: 1820: 1812: 1806: 1793: 1787: 1784: 1778: 1777: 1775: 1774: 1759: 1753: 1746: 1740: 1727: 1690:Superfecundation 1613:Vespertilionidae 1569: 1562: 1558: 1555: 1549: 1526: 1525: 1518: 1326:superfecundation 1270:vaginal delivery 1186:Low birth weight 880:Mohammadpur Umri 745: 721: 575:numerical prefix 556: 555: 295:may look similar 21: 5699: 5698: 5694: 5693: 5692: 5690: 5689: 5688: 5659: 5658: 5657: 5652: 5626: 5599:Conjoined twins 5593: 5565: 5547: 5541: 5511: 5483: 5481: 5468: 5466: 5448: 5446: 5442: 5427: 5423: 5415: 5413: 5409: 5370: 5351: 5277: 5275: 5215:10.1.1.378.4082 5109: 5107:Further reading 5104: 5103: 5092: 5088: 5077: 5073: 5040: 5036: 5027: 5025: 5012: 5011: 5007: 5001:Wayback Machine 4992: 4988: 4951: 4947: 4937: 4935: 4920: 4916: 4906: 4904: 4889: 4885: 4845: 4841: 4832: 4830: 4815: 4811: 4801: 4799: 4786: 4785: 4781: 4734: 4725: 4716: 4714: 4699: 4681: 4677: 4668: 4666: 4662: 4655: 4651: 4650: 4646: 4601: 4597: 4588: 4586: 4569: 4565: 4526:(2): CD008313. 4512: 4508: 4463: 4459: 4440: 4436: 4405:(5): 1095–101. 4391: 4387: 4377: 4375: 4371: 4360: 4354: 4350: 4319: 4308: 4299: 4297: 4284: 4283: 4279: 4270: 4268: 4255: 4254: 4250: 4241: 4239: 4226: 4225: 4221: 4211: 4209: 4192: 4188: 4181: 4159: 4155: 4145: 4143: 4126: 4122: 4108: 4104: 4065: 4061: 4024: 4020: 4010: 4008: 3999: 3998: 3994: 3985: 3983: 3948: 3944: 3905: 3901: 3891: 3889: 3882:himsamachar.com 3876: 3875: 3871: 3861: 3859: 3846: 3845: 3841: 3831: 3829: 3816: 3815: 3811: 3802: 3800: 3793:The Independent 3787: 3786: 3782: 3773: 3771: 3762: 3761: 3757: 3748:Wayback Machine 3738: 3734: 3724: 3722: 3707: 3703: 3664: 3660: 3637: 3619: 3615: 3606: 3604: 3600: 3573: 3567: 3563: 3554: 3552: 3530: 3523: 3517:Wayback Machine 3508: 3504: 3498:Wayback Machine 3489: 3482: 3445: 3441: 3434: 3405: 3401: 3392: 3390: 3379: 3370: 3363: 3341: 3326: 3317: 3315: 3311: 3270: 3264: 3260: 3251: 3250: 3246: 3234: 3232: 3166: 3162: 3109: 3105: 3057: 3053: 3043: 3041: 3026: 3022: 2979:Nature Genetics 2974: 2970: 2955: 2951: 2936: 2922: 2918: 2903: 2885: 2881: 2840:(30): 10604–9. 2826: 2822: 2782: 2778: 2739: 2735: 2704: 2700: 2655: 2651: 2606: 2602: 2593: 2591: 2578: 2577: 2573: 2564: 2562: 2549:(11): 913–921. 2535: 2531: 2515: 2514: 2508: 2506: 2495: 2491: 2454: 2450: 2441: 2439: 2424: 2423: 2419: 2409: 2407: 2402: 2401: 2397: 2352: 2345: 2338: 2324: 2320: 2311: 2309: 2300: 2299: 2295: 2285: 2283: 2274: 2273: 2269: 2260: 2258: 2241:"Italy: People" 2239: 2238: 2234: 2225: 2223: 2204: 2203: 2199: 2168: 2164: 2155: 2154: 2150: 2140: 2138: 2125: 2124: 2120: 2111: 2109: 2094: 2090: 2081: 2079: 2066: 2065: 2061: 2027: 2023: 1966:Smits, Jeroen; 1964: 1955: 1946: 1944: 1931: 1930: 1926: 1919: 1905: 1901: 1892: 1890: 1877: 1876: 1872: 1863: 1861: 1848: 1847: 1843: 1834: 1832: 1813: 1809: 1803:Wayback Machine 1794: 1790: 1785: 1781: 1772: 1770: 1765:. Nlm.nih.gov. 1761: 1760: 1756: 1747: 1743: 1737:Wayback Machine 1728: 1724: 1719: 1714: 1665:Litter (animal) 1630: 1570: 1559: 1553: 1550: 1543: 1527: 1523: 1516: 1494: 1481: 1443:Michael Gabbett 1385: 1373:Turner syndrome 1360: 1340: 1334: 1322: 1317: 1288: 1282: 1266: 1251: 1239: 1214: 1208: 1188: 1172: 1170:Miscarried twin 1155: 1143: 1137: 1135:Parasitic twins 1129:Lydia Fairchild 1112: 1106: 1066: 1064:Conjoined twins 1060: 1058:Conjoined twins 1038: 1032: 1030:Vanishing twins 1027: 990: 926: 892:multiple births 809: 803: 795:growth hormones 791:fertility drugs 771: 764: 753:gestational age 746: 737: 722: 707:conjoined twins 689:Conjoined twins 540:conjoined twins 522: 502:without a heart 494: 484:Nature Genetics 395: 380: 372:embryo transfer 349: 315: 214: 169: 121: 87:In contrast, a 39: 28: 23: 22: 15: 12: 11: 5: 5697: 5687: 5686: 5681: 5676: 5671: 5654: 5653: 5651: 5650: 5645: 5640: 5638:Vanishing twin 5634: 5632: 5628: 5627: 5625: 5624: 5623: 5622: 5614: 5607:Parasitic twin 5603: 5601: 5595: 5594: 5592: 5591: 5586: 5581: 5575: 5573: 5567: 5566: 5564: 5563: 5557: 5555: 5549: 5548: 5540: 5539: 5532: 5525: 5517: 5510: 5509:External links 5507: 5506: 5505: 5500: 5493: 5489: 5477:Taylor, Ally. 5474: 5454: 5432:TWINS Magazine 5421: 5381:(2): 430–436. 5363: 5349: 5336: 5283: 5251:(3): e447–53. 5236: 5208:(6): 1159–61. 5197: 5154: 5117: 5108: 5105: 5102: 5101: 5086: 5071: 5052:(6): 387–395. 5034: 5020:. 2015-10-01. 5005: 4986: 4945: 4914: 4883: 4850:Human Genetics 4839: 4809: 4779: 4723: 4697: 4675: 4644: 4595: 4563: 4506: 4457: 4434: 4399:Obstet Gynecol 4385: 4348: 4306: 4277: 4248: 4219: 4186: 4179: 4153: 4120: 4102: 4059: 4018: 3992: 3962:(2): 132–136. 3942: 3899: 3869: 3839: 3822:Times of India 3809: 3799:on 15 May 2009 3780: 3755: 3739:Linda Geddes: 3732: 3701: 3674:(4): 431–437. 3658: 3635: 3613: 3561: 3544:(5): 405–410. 3521: 3502: 3480: 3439: 3432: 3399: 3368: 3361: 3324: 3258: 3244: 3242: 3241: 3180:(2): 236–242. 3160: 3123:(6): 533–537. 3103: 3051: 3020: 2968: 2949: 2934: 2916: 2901: 2879: 2820: 2776: 2733: 2714:(3): 216–228. 2698: 2669:(2): 117–123. 2649: 2600: 2571: 2529: 2489: 2462:Fertil. Steril 2448: 2434:. 2007-07-02. 2417: 2395: 2366:(2): 179–187. 2343: 2336: 2318: 2293: 2267: 2253:. 2008-09-04. 2232: 2218:. 2008-09-04. 2197: 2178:(3): 189–202. 2162: 2148: 2118: 2088: 2059: 2037:(4): 599–609. 2021: 1953: 1924: 1917: 1899: 1885:. 2001-06-07. 1870: 1856:. 2007-11-12. 1841: 1807: 1788: 1779: 1754: 1741: 1721: 1720: 1718: 1715: 1713: 1712: 1707: 1702: 1697: 1692: 1687: 1682: 1680:Multiple birth 1677: 1672: 1667: 1662: 1657: 1652: 1647: 1642: 1637: 1631: 1629: 1626: 1572: 1571: 1530: 1528: 1521: 1515: 1512: 1493: 1490: 1486:situs inversus 1480: 1477: 1434:XX, and one a 1384: 1381: 1359: 1356: 1336:Main article: 1333: 1330: 1321: 1318: 1316: 1313: 1284:Main article: 1281: 1278: 1265: 1262: 1250: 1247: 1238: 1235: 1210:Main article: 1207: 1204: 1200:cerebral palsy 1187: 1184: 1180:vanishing twin 1171: 1168: 1154: 1151: 1141:Parasitic twin 1139:Main article: 1136: 1133: 1108:Main article: 1105: 1102: 1062:Main article: 1059: 1056: 1048:vanishing twin 1036:Vanishing twin 1034:Main article: 1031: 1028: 1026: 1023: 1014: 1013: 1010: 1007: 1004: 1001: 989: 986: 954: 953: 950: 947: 944: 925: 922: 888: 887: 877: 867: 805:Main article: 802: 799: 784:growth hormone 770: 767: 766: 765: 761:sagittal plane 747: 740: 738: 730:sagittal plane 723: 716: 711: 710: 703: 691: 685: 684: 681: 677:cerebral palsy 650: 644: 643: 640: 607: 601: 600: 593: 571: 567: 566: 563: 560: 521: 518: 493: 490: 394: 391: 379: 376: 361:zona pellucida 348: 345: 314: 311: 213: 210: 187: 186: 183: 180: 168: 165: 153:Southeast Asia 141:Central Africa 120: 117: 101:multiple birth 26: 9: 6: 4: 3: 2: 5696: 5685: 5682: 5680: 5677: 5675: 5672: 5670: 5667: 5666: 5664: 5649: 5646: 5644: 5641: 5639: 5636: 5635: 5633: 5629: 5621: 5620: 5615: 5613: 5610: 5609: 5608: 5605: 5604: 5602: 5600: 5596: 5590: 5587: 5585: 5582: 5580: 5577: 5576: 5574: 5572: 5568: 5562: 5559: 5558: 5556: 5554: 5550: 5545: 5538: 5533: 5531: 5526: 5524: 5519: 5518: 5515: 5504: 5501: 5498: 5494: 5490: 5480: 5475: 5465:on 2009-10-15 5464: 5460: 5455: 5445:on 2008-10-30 5441: 5437: 5433: 5426: 5422: 5412:on 2008-10-02 5408: 5404: 5400: 5396: 5392: 5388: 5384: 5380: 5376: 5369: 5364: 5360: 5356: 5352: 5346: 5342: 5337: 5333: 5329: 5324: 5319: 5314: 5309: 5305: 5301: 5297: 5293: 5289: 5284: 5274: 5270: 5266: 5262: 5258: 5254: 5250: 5246: 5242: 5237: 5233: 5229: 5225: 5221: 5216: 5211: 5207: 5203: 5198: 5194: 5190: 5186: 5182: 5177: 5172: 5168: 5164: 5160: 5155: 5151: 5147: 5143: 5139: 5135: 5131: 5127: 5123: 5118: 5115: 5112:Bacon, Kate. 5111: 5110: 5097: 5090: 5082: 5075: 5067: 5063: 5059: 5055: 5051: 5047: 5046: 5038: 5023: 5019: 5015: 5009: 5002: 4998: 4995: 4990: 4982: 4978: 4973: 4968: 4964: 4960: 4956: 4949: 4933: 4929: 4925: 4918: 4902: 4898: 4894: 4887: 4879: 4875: 4871: 4867: 4863: 4859: 4856:(2): 179–85. 4855: 4851: 4843: 4828: 4824: 4820: 4813: 4797: 4793: 4789: 4783: 4775: 4771: 4766: 4761: 4756: 4751: 4747: 4743: 4739: 4732: 4730: 4728: 4713:on 2009-01-06 4712: 4708: 4704: 4700: 4694: 4690: 4686: 4679: 4665:on 2016-03-04 4661: 4654: 4648: 4640: 4636: 4631: 4626: 4622: 4618: 4614: 4610: 4606: 4599: 4584: 4580: 4579: 4574: 4567: 4559: 4555: 4550: 4545: 4541: 4537: 4533: 4529: 4525: 4521: 4517: 4510: 4502: 4498: 4493: 4488: 4484: 4480: 4476: 4472: 4468: 4461: 4453: 4449: 4445: 4438: 4430: 4426: 4421: 4416: 4412: 4408: 4404: 4400: 4396: 4389: 4374:on 2011-12-15 4370: 4366: 4359: 4352: 4344: 4340: 4336: 4332: 4329:(2): 209–19. 4328: 4324: 4317: 4315: 4313: 4311: 4295: 4291: 4287: 4281: 4266: 4262: 4258: 4252: 4237: 4233: 4229: 4223: 4207: 4203: 4202:New scientist 4198: 4190: 4182: 4176: 4172: 4168: 4164: 4157: 4141: 4137: 4132: 4124: 4117: 4113: 4106: 4098: 4094: 4090: 4086: 4082: 4078: 4075:(3): 346–53. 4074: 4070: 4063: 4055: 4051: 4046: 4041: 4037: 4033: 4029: 4022: 4006: 4002: 3996: 3981: 3977: 3973: 3969: 3965: 3961: 3957: 3956:Twin Research 3953: 3946: 3938: 3934: 3930: 3926: 3922: 3918: 3914: 3910: 3903: 3887: 3883: 3879: 3873: 3857: 3853: 3849: 3843: 3827: 3823: 3819: 3813: 3798: 3794: 3790: 3784: 3769: 3765: 3759: 3752: 3751:New Scientist 3749: 3745: 3742: 3736: 3720: 3716: 3715:The Telegraph 3712: 3705: 3697: 3693: 3689: 3685: 3681: 3677: 3673: 3669: 3662: 3654: 3650: 3646: 3642: 3638: 3632: 3628: 3624: 3617: 3599: 3595: 3591: 3587: 3583: 3579: 3572: 3565: 3551: 3547: 3543: 3539: 3535: 3528: 3526: 3518: 3514: 3511: 3506: 3499: 3495: 3492: 3487: 3485: 3476: 3472: 3467: 3462: 3459:(12): 753–8. 3458: 3454: 3450: 3443: 3435: 3429: 3425: 3421: 3417: 3413: 3409: 3403: 3388: 3384: 3377: 3375: 3373: 3364: 3358: 3354: 3349: 3348: 3339: 3337: 3335: 3333: 3331: 3329: 3314:on 2016-06-03 3310: 3306: 3302: 3298: 3294: 3290: 3286: 3282: 3278: 3277: 3269: 3262: 3254: 3248: 3230: 3226: 3222: 3218: 3214: 3210: 3206: 3201: 3200: 3197: 3193: 3188: 3183: 3179: 3175: 3171: 3164: 3156: 3152: 3147: 3142: 3138: 3134: 3130: 3126: 3122: 3118: 3114: 3107: 3099: 3095: 3091: 3087: 3083: 3079: 3075: 3071: 3067: 3063: 3055: 3039: 3035: 3031: 3024: 3016: 3012: 3008: 3004: 3000: 2996: 2992: 2988: 2984: 2980: 2972: 2964: 2960: 2953: 2945: 2941: 2937: 2931: 2927: 2920: 2912: 2908: 2904: 2902:0-525-94465-6 2898: 2893: 2892: 2883: 2875: 2871: 2866: 2861: 2856: 2851: 2847: 2843: 2839: 2835: 2831: 2824: 2816: 2812: 2808: 2804: 2800: 2796: 2792: 2788: 2787:J. Med. Genet 2780: 2772: 2768: 2764: 2760: 2756: 2752: 2748: 2744: 2737: 2729: 2725: 2721: 2717: 2713: 2709: 2702: 2694: 2690: 2685: 2680: 2676: 2672: 2668: 2664: 2660: 2653: 2645: 2641: 2636: 2631: 2627: 2623: 2620:(3): 234–43. 2619: 2615: 2611: 2604: 2590:on 2007-09-21 2589: 2585: 2581: 2575: 2560: 2556: 2552: 2548: 2544: 2540: 2533: 2525: 2519: 2504: 2500: 2493: 2485: 2481: 2476: 2471: 2467: 2463: 2459: 2452: 2437: 2433: 2432: 2427: 2421: 2405: 2399: 2391: 2387: 2383: 2379: 2374: 2369: 2365: 2361: 2357: 2350: 2348: 2339: 2333: 2329: 2322: 2308:on 2016-03-04 2307: 2303: 2297: 2281: 2277: 2271: 2256: 2252: 2248: 2247: 2242: 2236: 2221: 2217: 2213: 2212: 2207: 2201: 2193: 2189: 2185: 2181: 2177: 2173: 2166: 2158: 2152: 2136: 2132: 2128: 2122: 2107: 2103: 2099: 2092: 2077: 2073: 2072:Go Ask Alice! 2069: 2063: 2056: 2052: 2048: 2044: 2040: 2036: 2032: 2025: 2017: 2013: 2008: 2003: 1998: 1993: 1989: 1985: 1982:(9): e25239. 1981: 1977: 1973: 1969: 1962: 1960: 1958: 1942: 1938: 1934: 1928: 1920: 1914: 1910: 1903: 1888: 1884: 1880: 1874: 1859: 1855: 1851: 1845: 1830: 1826: 1825: 1819: 1811: 1804: 1800: 1797: 1792: 1783: 1768: 1764: 1758: 1751: 1745: 1738: 1734: 1731: 1726: 1722: 1711: 1708: 1706: 1703: 1701: 1698: 1696: 1693: 1691: 1688: 1686: 1683: 1681: 1678: 1676: 1673: 1671: 1668: 1666: 1663: 1661: 1658: 1656: 1653: 1651: 1648: 1646: 1643: 1641: 1638: 1636: 1633: 1632: 1625: 1621: 1618: 1614: 1608: 1604: 1602: 1598: 1597:DNA profiling 1593: 1589: 1584: 1580: 1568: 1565: 1557: 1547: 1541: 1540: 1536: 1531:This section 1529: 1520: 1519: 1511: 1508: 1504: 1499: 1489: 1487: 1476: 1474: 1472: 1468: 1464: 1460: 1459:heterogonesis 1456: 1452: 1448: 1447:Nicholas Fisk 1444: 1439: 1437: 1433: 1430:. One was an 1429: 1421: 1417: 1412: 1408: 1406: 1402: 1401:heterogonesis 1398: 1394: 1389: 1380: 1378: 1374: 1368: 1366: 1355: 1353: 1349: 1345: 1339: 1329: 1327: 1312: 1310: 1306: 1305:environmental 1302: 1301:psychological 1298: 1294: 1287: 1277: 1275: 1271: 1261: 1259: 1255: 1246: 1243: 1234: 1232: 1228: 1218: 1213: 1203: 1201: 1197: 1193: 1183: 1181: 1177: 1167: 1165: 1161: 1150: 1148: 1142: 1132: 1130: 1126: 1122: 1118: 1111: 1101: 1099: 1095: 1091: 1087: 1078: 1074: 1070: 1065: 1055: 1053: 1049: 1044: 1037: 1022: 1018: 1011: 1008: 1005: 1002: 999: 998: 997: 995: 985: 983: 979: 975: 971: 967: 962: 960: 951: 948: 945: 942: 938: 934: 933: 932: 929: 921: 918: 916: 912: 908: 903: 901: 897: 893: 885: 884:Uttar Pradesh 882:, located in 881: 878: 875: 872:, located in 871: 868: 866: 862: 859: 858: 857: 854: 853:Josef Mengele 850: 846: 845:Cândido Godói 842: 838: 837:ethnic groups 834: 826: 825:Yoruba people 822: 818: 813: 808: 798: 796: 792: 787: 785: 780: 776: 762: 758: 757:coronal plane 754: 750: 744: 739: 735: 734:coronal plane 731: 727: 726:co-incubation 720: 715: 714: 708: 704: 702: 699: 697: 692: 690: 687: 686: 682: 680: 678: 674: 669: 666: 664: 661: 655: 651: 649: 646: 645: 641: 639: 637: 633: 628: 626: 622: 621:almost always 618: 617:amniotic sacs 612: 608: 606: 603: 602: 598: 597:fertilisation 594: 592: 588: 584: 583:amniotic sacs 580: 576: 572: 569: 568: 564: 561: 558: 557: 554: 552: 547: 545: 541: 536: 528: 524: 517: 515: 510: 507: 503: 499: 489: 486: 485: 480: 475: 472: 468: 460: 456: 451: 447: 444: 439: 437: 433: 429: 425: 420: 417: 408: 407:amniotic sacs 404: 399: 390: 387: 383: 375: 373: 369: 364: 362: 358: 354: 344: 342: 338: 334: 330: 327: 323: 319: 310: 306: 304: 298: 296: 292: 288: 284: 279: 277: 273: 269: 265: 261: 257: 253: 249: 245: 242: 238: 234: 226: 218: 209: 207: 203: 199: 197: 193: 184: 181: 178: 177: 176: 173: 164: 162: 156: 154: 150: 146: 145:South America 142: 138: 134: 133:phytoestrogen 130: 126: 125:Yoruba people 116: 114: 110: 106: 102: 98: 94: 90: 85: 83: 79: 75: 71: 67: 63: 59: 55: 48: 43: 37: 33: 19: 5618: 5560: 5543: 5482:. 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Retrieved 1757: 1749: 1744: 1725: 1710:Virtual twin 1640:Doppelgänger 1622: 1609: 1605: 1575: 1560: 1551: 1544:Please help 1539:verification 1532: 1503:cryptophasia 1495: 1482: 1475: 1440: 1424: 1386: 1369: 1364: 1361: 1341: 1323: 1309:human nature 1289: 1267: 1252: 1240: 1231:polycythemic 1223: 1192:birth weight 1189: 1173: 1156: 1144: 1113: 1082: 1039: 1019: 1015: 991: 981: 963: 955: 937:West African 930: 927: 919: 904: 899: 889: 832: 830: 788: 772: 769:Demographics 700: 693: 670: 667: 659: 657: 629: 627:have fused. 620: 614: 590: 562:Description 548: 537: 533: 523: 511: 495: 482: 476: 464: 440: 421: 416:fingerprints 412: 388: 384: 381: 365: 352: 350: 328: 325: 321: 317: 316: 307: 299: 280: 267: 263: 255: 243: 240: 236: 232: 231: 200: 195: 191: 188: 174: 170: 157: 122: 113:doppelgänger 107:. Unrelated 104: 96: 86: 77: 65: 53: 52: 5648:Mixed twins 5169:(1): 43–7. 5128:(1): 72–6. 4965:(1): 81–5. 4938:28 February 4907:28 February 4802:28 February 4169:. pp. 3453:J Perinatol 2503:WonderQuest 2431:EurekAlert! 2141:11 November 2131:China Daily 1675:Mixed twins 1507:Idioglossia 1388:Monozygotic 1348:mixed twins 1338:Mixed twins 1332:Mixed twins 1242:Stillbirths 1237:Stillbirths 1176:miscarriage 974:anovulation 900:monozygotic 663:monozygotic 625:blastocysts 587:monozygotic 500:twin fetus 459:Scott Kelly 318:Monozygotic 258:, form two 252:sperm cells 109:look-alikes 66:monozygotic 18:Monozygotic 5663:Categories 5546:conditions 5484:2018-03-30 5469:2008-10-18 5449:2008-10-06 5416:2008-10-02 5278:2008-10-06 5245:Pediatrics 5028:2018-09-05 4833:2023-04-29 4717:2008-09-30 4669:2015-04-18 4589:2012-04-07 4300:2015-10-26 4290:BabyCentre 4271:2015-10-23 4242:2015-10-23 3986:2013-08-10 3892:23 October 3862:23 October 3832:23 October 3803:2009-08-06 3774:2009-08-06 3607:2008-09-29 3555:2008-09-29 3393:2008-10-10 3383:"Twinning" 3318:2016-05-03 3276:The Lancet 3268:"Twinning" 3235:7 February 2965:: 147–159. 2594:2008-09-30 2565:2008-10-02 2509:2007-03-22 2442:2019-08-05 2312:2013-09-16 2261:2008-10-02 2226:2008-10-02 2112:2022-04-07 2082:2022-04-07 1947:2022-04-07 1893:2008-09-29 1864:2008-09-29 1835:2008-09-29 1773:2016-06-16 1717:References 1695:Twin study 1685:Multiverse 1670:Look-alike 1554:March 2024 1377:karyotypes 1286:Twin study 935:She is of 506:polar body 471:epigenetic 432:phenotypes 428:aneuploidy 357:blastocyst 248:fertilized 208:of twins. 149:South Asia 119:Statistics 5643:Chimerism 5375:Evolution 5359:123390922 5210:CiteSeerX 4707:172964621 4540:1469-493X 4477:: i4353. 4136:The Times 3645:1358-8702 3305:208792233 3137:1058-0468 3044:8 January 3015:230986741 2999:1546-1718 2382:1355-4786 1645:Evil twin 1583:ovulation 1535:citations 1418:breed in 1196:premature 1160:triploidy 1125:DNA tests 1117:mosaicism 1104:Chimerism 978:clomifene 833:dizygotic 817:ere ibeji 801:Ethnicity 797:in food. 642:Days 4-8 577:for two) 551:placentas 514:triploidy 378:Incidence 347:Mechanism 326:identical 264:dizygotic 241:fraternal 233:Dizygotic 97:singleton 78:dizygotic 62:pregnancy 58:offspring 5553:Zygosity 5395:15068359 5332:17576931 5273:20498737 5265:17766488 5193:23507167 5150:19112883 5142:10073913 5066:16690234 5022:Archived 4997:Archived 4870:17165045 4827:Archived 4796:Archived 4792:CBC News 4774:30811910 4583:Archived 4558:27075527 4501:27599496 4452:Archived 4448:BBC News 4429:22015878 4343:23062593 4294:Archived 4265:Archived 4236:Archived 4206:Archived 4140:Archived 4097:19195460 4089:18307076 4054:24304051 3980:Archived 3976:11931691 3937:45092501 3826:Archived 3768:Archived 3744:Archived 3719:Archived 3696:23862192 3653:36287045 3598:Archived 3594:11968567 3588:: 1–17. 3550:16779988 3513:Archived 3494:Archived 3475:16281049 3410:(2004). 3387:Archived 3297:12957099 3229:Archived 3225:85215225 3196:12571155 3155:22460080 3038:Archived 3007:33414551 2944:43894450 2911:40396458 2874:16009939 2807:24123875 2771:31844710 2763:11113914 2644:18669930 2559:Archived 2555:10589400 2518:cite web 2484:19217091 2436:Archived 2390:10336022 2280:Archived 2255:Archived 2220:Archived 2135:Archived 2106:Archived 2076:Archived 2051:18063108 2016:21980404 1976:PLOS ONE 1941:Archived 1939:. 1999. 1887:Archived 1858:Archived 1829:Archived 1799:Archived 1767:Archived 1733:Archived 1628:See also 1432:intersex 1428:chimeras 1416:Hereford 1365:in utero 1344:biracial 1147:parasite 1121:intersex 1077:Thailand 1052:chimeric 861:Igbo-Ora 632:placenta 611:placenta 579:chorions 424:genotype 403:placenta 291:siblings 272:siblings 268:biovular 202:Zygosity 196:in utero 192:in utero 105:multiple 56:are two 5684:Zoology 5679:Sibling 5619:in fetu 5403:9460009 5323:1904168 5300:Bibcode 5232:9176461 5185:1488855 4981:6540028 4928:Gannett 4897:Reuters 4878:3343267 4823:YouTube 4630:1013354 4549:6464533 4492:5013231 4420:3202294 4378:12 June 3929:7437372 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