Interbreeding doubles genetic risk


First cousins who marry run twice the risk of having a child with genetic abnormalities, according to the findings of a study in the English city of Bradford that was published Friday in The Lancet.

The city, whose population has a high proportion of South Asian immigrants and their descendants, served as a microcosm for examining the risk of blood relative couplings. About 37 percent of marriages among people of Pakistani origin in the study involved first cousins, compared to less than 1 percent of “British unions,” said the researchers.

Eamonn Sheridan of the University of Leeds led a team that pored over data from the “Born in Bradford” study, which tracked the health of 13,500 babies born at the city’s main hospital between 2007 and 2011. Out of 11,396 babies for whom family details were known, 18 percent were the offspring of first-cousin unions, mainly among people of Pakistani ancestry.

A total of 386 babies, or 3 percent, were born with anomalies ranging from problems in the nervous, respiratory and digestive systems to urinary and genital defects and cleft palates. This rate was nearly twice the national average, the study said.