Yes, twins can have twins, but the likelihood depends on several factors, primarily the type of twins they are (fraternal or identical) and family history.
Understanding Twin Types and Heredity
There are two main types of twins:
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Fraternal (dizygotic) twins: These twins result from two separate eggs being fertilized by two separate sperm. They are genetically no more similar than any other siblings. According to the American Society for Reproductive Medicine, women who are fraternal twins have a higher chance (1 in 60) of having twins themselves compared to the general population. Men who are fraternal twins also have a slightly increased chance (1 in 125) of fathering twins. This increased likelihood is due to a genetic predisposition towards hyperovulation (releasing more than one egg during a menstrual cycle) that can be inherited. As stated in various sources, fraternal twinning does run in families and doesn't necessarily skip a generation.
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Identical (monozygotic) twins: These twins develop from a single fertilized egg that splits into two embryos. They share the same genetic material. Identical twinning is not typically hereditary; the chance of having identical twins remains relatively consistent across families (about 1 in 250).
Increased Risk Factors for Twin Births
Several factors influence the chances of having twins, including:
- Family history: As discussed above, a family history of fraternal twins increases the probability of having twins.
- Maternal age: Older mothers have a slightly higher chance of releasing multiple eggs.
- Fertility treatments: These treatments often increase the likelihood of multiple pregnancies.
Conclusion
While identical twins themselves cannot pass on the trait of identical twinning, fraternal twins can pass on a genetic predisposition towards having fraternal twins. Therefore, a woman who is a fraternal twin has a statistically higher chance of having twins, and the same is true (although to a lesser extent) for a man who is a fraternal twin.
