Children of First Cousin Couples have Higher Birth Defect Risk

Couples, who are first cousins, are at twice the risk of having a baby with birth defects like heart or lung abnormalities, a new study reported.

The study was based on data from over 11,000 births in Bradford, U.K. between 2007 and 2011. In the study group, about 2000 babies were born to parents who were first cousins- most were from the city's large Pakistani population. These children had a six percent risk of a serious congenital birth defect when compared to three percent risk in the general population.

Consanguinity is a common social trend in a fifth of the world's population. Many cultures in the Middle East, West Asia and North Africa support marriages between cousins who are related by blood.

"It is important to note that the absolute increase in risk is small (from 3% to 6%), meaning that only a small minority of babies born to couples who are blood relatives or older mothers (older White British mums have an increase in risk from 2% to 4%) will develop a congenital anomaly," said Eamonn Sheridan from the University of Leeds in the UK, lead author of the study, according to a news release.

A similar risk was seen in white mothers who were over 34 years old, researchers said. In the study, children born to couples who weren't related by blood but had babies at an older age also had an increased risk of serious birth defects.

"This is the first study that has been able to explore all causes of congenital anomaly in a population where there are sufficient numbers in both consanguineous and non-consanguineous groups to come to reliable conclusions. Clear and accessible information on these small but significant avoidable risks should be widely disseminated to local communities and be included as part of antenatal counselling and in the planning of healthcare services," said Neil Small from the University of Bradford, co-lead author of the study.

The study is published in the journal Lancet.