Most people balk at the idea of first cousins marrying each other, but the practice isn't as forbidden or as risky as you may think.
In other parts of the world, marrying your first cousin is socially acceptable; in the United States, it's a bit more taboo. But in 21 states, it is legal for first cousins to get married, according to the National Conference of State Legislatures' website (NCSL). Professor Alan Bittles of Murdoch University and Edith Cowan University in Australia has studied cousin marriages for the past 30 years. He says it's likely 10.4 percent of people worldwide are married to a close relative or are the children of such a marriage. "This equates to over 700 million people," Bittles says.

Where It's Legal, Where It's Not
According to the NCSL, cousin marriage is legal in: Alabama, Alaska, California, Colorado, Connecticut, District of Columbia, Florida, Georgia, Hawaii, Maryland, Massachusetts, New Jersey, New Mexico, New York, North Carolina (in North Carolina, first-cousin marriage is legal, but double-cousin marriage is prohibited), Rhode Island, South Carolina, Tennessee, Texas, Vermont and Virginia.

In Arizona, Illinois, Indiana, Maine, Utah and Wisconsin, first-cousin marriage is allowed under certain circumstances:

  • Arizona: If both are 65 or older, or one is unable to reproduce
  • Illinois: If both are 50 or older, or one is unable to reproduce
  • Indiana: If both are at least 65
  • Maine: If couple obtains a physician's certificate of genetic counseling
  • Utah: If both are 65 or older, or if both are 55 or older and one is unable to reproduce
  • Wisconsin: If the woman is 55 or older, or one is unable to reproduce
First-cousin marriage is prohibited in: Arkansas, Delaware, Idaho, Iowa, Kansas, Kentucky, Louisiana, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, South Dakota, Washington, West Virginia and Wyoming.

Health Risks to Offspring
The assumption that children of first cousins are likely to suffer from health problems has been around for centuries, Bittles says. "Although there has been a tradition of cousin marriage among royalty, major land-owning families and some business dynasties, the highest rates of consanguinity [cousin marriage] are actually among the rural poor whose general health status often is marginal," he says. "Under these circumstances, unless appropriate allowance is made for adverse family socioeconomics, just about all health problems have simply been blamed on consanguinity, even though there usually is no specific evidence of a causal relationship between consanguinity and the disorder in question."

Bittles' studies have found that the instance of major health problems in the offspring of cousins is much lower than you may think. "[There is] an excess risk of early death or major ill health of 3.5 percent among the children of first cousins—which is much less than [many people] would have anticipated," Alan says."In general terms, our studies have shown that the health risks attributed to consanguinity have been exaggerated."

Reverse the Bans?
Because of the modest health risks and access to genetic counseling and premarital advice for cousin couples, Bittles says state bans on first-cousin marriage appear to be unnecessary. "Given decreasing family sizes and ever-increasing educational, employment and social mobility, it seems almost inevitable that the prevalence of cousin marriage in the U.S. and other Western countries will decline," he says. "There is certainly no evidence that if the states which currently ban first cousin marriage were to repeal their legislation, a great demand for such marriages would result."

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