Doesn’t it seem like twins are becoming more common? They are!
Who is most likely to have twins?
- Women who are non-identical twins themselves
- Women who have already had a set of non-identical twins
- Women with a female family member who has had non-identical twins
- Women of African descent
Well, those characteristics probably haven’t changed much in the last decades, but here is one that has:
- Women using fertility drugs
Scarlett Johansson, part of the ensemble cast of the new movie “He’s Just Not that Into You,” has a twin brother named Hunter. He is also an actor.
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How does twinning occur?
Twins arise when either two eggs are fertilized (fraternal twins) or one fertilized egg splits before it starts to develop (identical twins.) Identical twins are always the same sex and have the same genetic make-up, while fraternal twins are only as alike as any other pair of siblings.
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Identical twins: Identical twinning occurs randomly; every pregnancy has about a one in two hundred and forty chance of identical twins. A woman who has identical twins in her family is not particularly likely to have twins, since identical twinning is a random event and not determined by a familial tendency.
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Fraternal twins: Since the tendency for the mother to release multiple eggs at once is genetic, fraternal twins run in families and are more common in certain races and ethnicities. The male partner can’t increase the chance of twinning, since he doesn’t influence the number of eggs in his mate’s ovulation. Fertility drugs increase the odds of twins (or triplets—or more) primarily by causing the release of multiple eggs per cycle.
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