NEW ORLEANS — The impact of overweight on in vitro fertilization success rates may be age related, Dr. Megan Sneed reported at the annual meeting of the American Society for Reproductive Medicine. Her findings may explain some inconsistencies in the literature on this topic.
“Young patients in particular should be counseled to lose weight to improve their chances with in vitro fertilization, but for women over age 35, weight loss should not delay fertility treatment because their ovarian reserve is in decline,” advised Dr. Sneed of Fertility Centers of Illinois, Chicago, and Advocate Lutheran General Hospital in Park Ridge, Ill.
In a retrospective review of 1,273 fresh in vitro fertilization (IVF) cycles, Dr. Sneed found that body mass index (BMI) did not appear to significantly impact overall outcome—there was no significant difference in clinical pregnancy rate per cycle between normal weight (38.6%), overweight (36.8%), and obese (35.1%) patients. However, when patients' ages were factored into the analysis, overweight and obesity had a pronounced negative influence on the fertility of younger women, with a declining impact in women of older ages.
Specifically, in women aged 20 years, clinical pregnancy rates were found to be as high as 80% per cycle in the normal-weight group, while these rates decreased by as much as 25% in women who were overweight, and by as much as 50% in those who were obese, she said. A nearly identical trend was seen in the 25-year-old age group, while in the 30-year-old group the effect of obesity was much less pronounced, but still present, she said. In this latter group, women with normal BMIs had clinical pregnancy rates of up to 55%, which decreased to as low as 40% in the overweight group and 30% in the obese group. By age 35, there was virtually no impact of BMI on IVF outcome, with clinical pregnancy rates between 35% and 40% at all BMI ranges.
“I believe that these data may change recommendations for weight loss at some IVF centers,” Dr. Sneed said in an interview. “Many centers recommend weight loss to all patients undergoing IVF in an attempt to increase success rates. But in patients over 35, any delay in treatment for weight loss may result in a loss of valuable time since the impact of aging in this group appears to have a more profound effect on IVF outcomes than does weight.”