Genetics / Research states that there is little chance that children of first cousins will suffer from birth defects
by Tamara Traubman
Marriage of first cousins is considered, especially in Western society, a wrong practice and is often accompanied by severe social stigmas. However, recently scientists reported that contrary to popular belief, first cousins can give birth to children without much risk of birth defects and genetic diseases. "There is no biological reason to discourage cousins from marrying," said the head of the research team, Robin Bennett, president of the US National Society for Genetic Counseling, in an interview from the University of Washington.
According to the report, in the general population, the risk that a child will be born with a serious problem, such as cystic fibrosis, is 4-3%. When it comes to cousins, this risk increases by 2.8-1.7%, although the risk is almost double, "the data are not considered significant enough to not encourage cousins to have children," Bennett said.
"In terms of general risks in life, it is not very high," said Prof. Arno Motulsky, a pioneer of medical genetics and a senior member of the research team, in a statement accompanying the publication of the report. "Even in the worst case, a 7% risk," he said, " Still, in 93% of the cases, nothing will happen."
Bennett said that the additional risk comes from hereditary defects in genes called recessives, which have no effect on a person carrying one copy of the gene, but will cause disease when a person inherits two copies of the gene, one from each parent.
When two carriers with the same recessive copy have children, the child has a one in four chance of inheriting two copies of the gene and being born sick. Cystic fibrosis and Tay-Sachs, for example, are caused by recessive genes. Unrelated people carry fewer similar genes, so their risk of disease caused by recessive genes is slightly lower.
The researchers noted that there are genetic diseases, such as Huntington's disease (a degenerative disease that erupts in adulthood, for which there is no cure), for which the patients' risk of passing the disease on to their children is 50% much higher than that of cousins giving birth to a child with a birth defect or genetic disease. At the same time, no one disputes the right of Huntington's patients to have children.
24 states in the US have laws prohibiting first-degree cousins from marrying, and seven other states have restrictive laws requiring genetic counseling. European countries have no such restrictions, and among some groups in Israel and other countries in the Middle East, Africa, and Asia, marriage between cousins is Rather the preferred option. "In some parts of the world," the report states, "60-20% of all marriages are between biological relatives."
The team's conclusions, published in the April issue of the medical journal "Genetic" Counseling, are based on a review of six studies involving thousands of participants, conducted in the years 2000-1965 and additional medical literature. Bennett says that the panel was convened "because of the widespread misconceptions regarding the actual level of risk for the offspring of first cousins. There are quite a few doctors who advise such couples to end the pregnancy with an abortion."
According to the new report, doctors should advise cousins who want to have children in accordance with the existing recommendations regarding the ethnic group and family history. No additional special genetic tests are necessary.
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