DNA

You Could Be Your Own Twin

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You've probably heard someone say they "ate their twin in the womb." (If you haven't, you should get some weirder friends). The good news is that when a twin disappears in utero, it isn't because the sibling ate it. The reality is less creepy, but still quite bizarre: the disappearing twin often becomes part of the other.

Related: Explaining The Science Of Twins

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With You Always

Vanishing twin syndrome, as its called, occurs when a twin dies in utero, usually as a fertilized egg early in a pregnancy. Many different things can happen afterward: the mother can miscarry, or the fetal tissue can be absorbed by the mother's body, the placenta, or even the remaining twin. When the latter happens, the surviving baby is born with two genetic signatures, making it what's known as a tetragametic chimera.

Related: Mysterious Mirror Twins

Genetic Difficulties

The consequences of this condition can seem quite strange, especially in a world where we rely on the accuracy of DNA testing. One famous case was that of Lydia Fairchild, who ran into trouble in 2002 when she was applying for public assistance. A maternity test determined that she wasn't mother of the children she had definitely given birth to. After a long court battle, the "real" mother was revealed to be her unborn twin, whose DNA resided in her body.

Related: 97% Of Your Genome Is Junk DNA

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Key Facts In This Video

  1. A chimera is someone with multiple sets of DNA. 00:28

  2. It's estimated that about 1 in 8 single childbirths actually starts as a multiple pregnancy. 01:51

  3. Chimerism makes it possible for someone to give birth to a child, then fail a genetic maternity test related to that child. 02:06

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