Cousins dating first cousins
'' Somehow, this hasn't become general knowledge,'' even among doctors, he said.
Twenty-four states have laws forbidding first cousins from marrying, and seven states have limits like requiring genetic counseling.
Although the increase represents a near doubling of the risk, the result is still not considered large enough to discourage cousins from having children, said Dr.
Arno Motulsky, a professor emeritus of medicine and genome sciences at the University of Washington, and the senior author of the report.'' In terms of general risks in life it's not very high,'' Dr. Even at its worst, 7 percent, he said, ''93 percent of the time, nothing is going to happen.'' The report is in today's issue of The Journal of Genetic Counseling.'' As genetic advisers,'' Dr.
First cousins are somewhat more likely than unrelated parents to have a child with a serious birth defect, mental retardation or genetic disease, but their increased risk is nowhere near as large as most people think, the scientists said.
In the general population, the risk that a child will be born with a serious problem like spina bifida or cystic fibrosis is 3 percent to 4 percent; to that background risk, first cousins must add another 1.7 to 2.8 percentage points, the report said.
Motulsky said, ''we give people all the various possibilities and risks and leave it up to them to make a decision.
Some might decide a doubling of the risk is not something they want to face.'' He and his colleagues said no one questioned the right of people with genetic disorders to have children, even though some have far higher levels of risk than first cousins.
The report made a point of saying that the term ''incest'' should not be applied to cousins but only to sexual relations between siblings or between parents and children.Motulsky said researchers did not know why marriage between cousins was viewed with such distaste in the United States.He said some of the revulsion might have stemmed from the eugenics movement, which intended to improve the human race by deciding who should be allowed to breed.Estimates of marriages between related people, which include first cousins and more distant ones, range from less than 0.1 percent of the general population to 1.5 percent.In the past, small studies have found much higher rates in some areas.
The movement flourished in this country early in the 20th century.