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How Common Are Twins?Fraternal and IdenticalTwin pregnancies are either fraternal or identical. Fraternal twins share the same womb, but come from different ovum. Genetically, fraternal twins are as alike as any pair of siblings. Identical twins on the other hand, come from the same fertilized ovum and therefore share the same genetic makeup. The ratio of fraternal twin to single births varies from country to country. The highest incidence occurs in the Yoruba tribe of Nigeria where 46 of every 1000 pregancies involves fraternal twins. The lowest is in Japan, where the incidence of fraternal twinning is 4 per 1000. America and other European countries have about the same rate of 11 to 12 per 1000 births. The ratio of identical twin to single births is constant across countries and nationalities. About 3 out of every 1000 births involves identical twins. Scientists don't know why some pregancies involve identical twins and others do not, but it seems to be independent of such issues as heredity and diet. |
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Multiple Births on the IncreaseIncidences of multiple birth pregnancies have increased by 8% in the past 10 years. The increase has been attributed to later pregnancies by working mothers, which are more likely to result in twin births and the increased use of fertility drugs. "Twins and even triplet births are much more common these days, " says nurse Denise Schoeder of St. Judes hospital in Beaverton, Illinois. "Fortunately we are much better equipped to handle the special complications that arise with these type of pregnancies than we were, even five years ago." Statistics bear this out. Complications resulting from low birthweight babies (a common occurence with multiple births) are down 25% in the past ten years. In Dade County, Florida, two quadruplets have been born in the past 18 months. "I think we'll need to increase the size of our marternity ward if this keeps up," says Dr. Lawrence Jacobs of Miami Community Hospital. Sociologists worry about the effect of these multiple births on families and parents. "Parents usually prepare for a single child. When they're suddenly faced with a larger family than expected, it can cause stress and tension." reports a study recently published in the American Journal of Family Sociology. Nonetheless, parents seem to recover from the surprise. "There's an initial shock," reports Schoeder, "but after they get over that, parents are usually very pleased. In fact, they begin to see the humor in the situation. I think we tend to underestimate the coping abilities of parents." |
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