Overweight mothers may be more likely to have infertile sons, Danish researchers report.
Their study included 9,232 men and women aged 31 to 34. Among this group, 10 percent were born to underweight mothers, having a body mass index below 18.5; 77 percent to normal weight mothers; and 13 percent to overweight or obese mothers, with a pre-pregnancy B.M.I. above 25.
By examining records of infertility diagnosis and treatment, the scientists found that sons born to overweight mothers were 40 percent more likely to be infertile than those born to mothers of normal weight. Sons with underweight mothers had no increased rates of infertility, and a mother’s weight had no effect on the fertility of her daughters. The study, published in AOGS, controlled for maternal age, smoking, alcohol consumption, socioeconomic status and other factors.
The reason for the association is unknown, but the authors suggest that being overweight is an indication of hormonal imbalance, which could interfere with prenatal development of the male reproductive system.
The lead author, Dr. Linn H. Arendt, an obstetrician at Aarhus University in Denmark, said that being overweight in pregnancy is unhealthy for several reasons, and that most women are aware that obesity poses risks. She said that this is the first study to show an association between maternal B.M.I. and infertility in adult sons, but that she would not make a point of warning women about this issue.