Attitudes toward marriage between blood relatives vary considerably across all cultures, but whatever the traditions of different cultures, there is a serious health concern regarding consanguinity (a relationship between blood relatives) - marriage between first cousins can more than double the risk of giving birth to a baby with a congenital anomaly such as heart or lung defects, or down syndrome, according to a study published in The Lancet. And this practice is not uncommon in some parts of the world in fact, it s actively encouraged in the Middle East, accounting for more than half of all marriages.
As frightening as this increased risk may seem, we should point out that the absolute risk is not so great: In a study of more than 11,000 offspring within the large Pakistani community in the UK, marriages between blood relatives (typically first and second cousins) were associated with a 3- to 6 percent increased risk of Down syndrome and heart and lung defects; however, these did account for nearly one-third of birth defects in babies of Pakistani origin.
The study also found that older British mothers - those 34 years or older - had an increased risk of birth defects. In fact, only a small minority of babies born to couples who are blood relatives or older mothers (older White British moms have an increase in risk from 2% to 4%) will develop a congenital anomaly. says lead author of the study, Eamon Sheridan of the University of Leeds, U.K.
The risks among closely-related parents were almost double the national rates: 305 per 10,000 live births showed birth defects, compared to the national rate of 165 per 10,000 live births. Maternal smoking, alcohol consumption, and obesity were not identified as risk factors for birth defects in this cohort.
ACSH s Dr. Gilbert Ross noted that Women are having babies later on in life in recent years, at least in America. I believe most of them are aware of some increased risk of adverse outcomes as they get past 35 years, and certainly past 40. But that is not a valid reason for deciding not to bear children, given the small increased risk, at least according to this study. Obviously, this concern is one that couples planning a family will take into account, along with many others.