Odds of Consecutive Twin Births

Having twins isn't as rare as it once was, with the increase in assisted reproductive technology, or ART. Having one set increases your odds of having another twosome. But having two sets of twins in a row still qualifies as unusual. If you have one set of twins, your odds of naturally producing a consecutive set is just 1-in-1,600, statistician Andrew Swift of the University of Nebraska at Omaha reported to Livewell Nebraska.

  1. Types of Twins

    • Twins come in two varieties: identical twins, which start life as one fertilized egg that splits at an early stage of development, and fraternal twins, which develop from two separate eggs released and fertilized at the same time. Identical twins are always the same sex and look very much alike. Fraternal twins can be a boy-girl pair or two boys or two girls. Fraternal twins won't resemble one another any more than any other two siblings, however, because they're produced from two different eggs and sperm. Fraternal twins occur more often than identical twins.

    Natural Twinning Rates

    • The natural overall twinning rate, discounting the rise in twins from artificial methods, is 1-in-80, psychologist and director of the Twin Studies Center at California State University Nancy Segal reports to National Geographic. The Centers for Disease Control and Prevention reports that the twinning rate in 2009 in the United States was one in 30 births. Women of certain genetic backgrounds have a higher chance of having consecutive sets of twins. In the United States, black women have the highest incidence of twin births; Asian women have the lowest. West Africans are 10 times more likely to have twins than Chinese or Japanese women, according to the Scientific American.

    Assisted Reproductive Technology

    • Utilizing assisted reproductive technology, or ART, increases your risk of having consecutive sets of twins. Around 65 percent of all twins born in the United States were conceived though ART, according to a 2009 article in the "New York Times." Although the reason for the increased risk of fraternal twins is obvious -- if you produce more than one egg, you have a higher chance of having more than one baby -- the risk of having identical twins is also higher with in vitro fertilization, or IVF, procedures. As many as 10 to 12 percent of ART births are identical twins, the Proactive Genetics website reports, probably because the IVF procedure makes the embryo more likely to split. Around 30 percent of all ART births are twins, according to Baby Zone.

    Risk Factors

    • Some natural factors also increase your chances of having several sets of twins. Women age 37 and older have four times the chance of having fraternal twins than an 18-year-old because they're more likely to release two eggs at one time, Australian researchers on twin studies Nick Martin and Grant Montgomery reported in the March 2002 "Scientific American." After one set of twins, a woman's chance of having another set quadruples, obstetrician Dr. Stephen P. Emery of the Cleveland Clinic Foundation explains to Baby Zone. The chance of fraternal twins comes from the mother's side, not the father's. The rate of identical twins doesn't appear to be influenced by heredity.

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