Fertility Woes For Obese Couples

8 March 2007
Fertility Woes For Obese Couples
by George Atkinson

The journal Human Reproduction reports that if both partners in a couple are overweight, they will have to wait considerably longer before successfully conceiving a child. The findings, based on a Danish study of nearly 50,000 couples, show that if both partners were obese the chances of the couple having to wait for more than a year before the woman became pregnant were nearly three times higher than for a normal weight couple. If both partners were only overweight, the likelihood they would have to wait longer than a year was 1.4 times higher.

Previous studies had already shown that weight can adversely affect fertility, but this is the first study to look at the effect of weight on fertility in couples. Study leader, Cecilia Ramlau-Hansen, warned that increasing levels of obesity could have major implications for population levels. "If overweight and obesity actually is a cause of subfecundity [sub-fertility], and if the obesity epidemic continues, this reduced capacity to reproduce could become a serious public health problem," she said. Sub-fertility is defined as a waiting time to pregnancy of more than 12 months from the time a couple starts to have unprotected sex with an intention to conceive.

Interestingly, underweight partners were also a strong indicator of sub-fertility. "Underweight combined with obese partners, especially underweight men, seemed to cause additional pregnancy delays. The combination of an underweight man and obese woman was associated with a risk of sub-fertility nearly four times higher compared to a normal weight couple," explained Ramlau-Hansen.

While the results indicate that overweight and obesity are causes of sub-fertility, the study notes that there might be an unknown underlying factor, such as a disease or genetic factors, that causes both the overweight/obesity and the sub-fertility, and this could only be established in a future randomized trial. Additionally, Ramlau-Hansen speculated that frequency of intercourse might be a factor. "Since reliable data on frequency and timing of sexual intercourse were not available, we cannot exclude the possibility that infrequent intercourse has delayed conception in overweight and obese couples," she noted.

Previous studies have shown that a man's Body Mass Index (BMI) is associated with semen quality and levels of reproductive hormones, and that, in women, obesity can adversely affect ovulation, conception, implantation and early fetal development. Ramlau-Hansen's advice to overweight and obese couples that want to have a child is that losing weight might decrease their waiting time to pregnancy.

Related articles:
Fertility Plummets With Fatness
Obesity Hormone Linked To Penis Function

Source: European Society for Human Reproduction and Embryology