Overweight mothers are more likely to have infertile sons, Danish researchers report.
Their study included 9,232 men and women aged 31 to 34 years. In this group, 10 percent of underweight mothers were born with a body mass index below 18.5. 77 percent of mothers of normal weight; and 13 percent for overweight or obese mothers with a B.M.I. before pregnancy. over 25.
When examining the records of the diagnosis and treatment of infertility, the scientists found that sons of overweight mothers were 40 percent more likely to be infertile than sons of mothers of normal weight. Sons with underweight mothers did not have increased infertility rates, and a mother's weight did not affect her daughters' fertility. The study, published in AOGS, controlled maternal age, smoking, alcohol consumption, socio-economic status, and other factors.
The reason for the association is unknown, but the authors suggest that obesity is an indication of a hormonal imbalance that could affect prenatal development of the male reproductive system.
The lead author, Dr. Linn H. Arendt, 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 is a risk. She said this is the first study to show an association between maternal B.M.I. and infertility in adult sons, but that she would not warn women of this problem.