Weight loss interventions -- dramatic reduction in caloric intake, increased activity during the periconceptual period -- put stress on the reproductive system and could lead to failure even when using assisted reproductive techniques.
Professor Richard Legro of the Department of Obstetrics and Gynecology at Penn State University College of Medicine warned that the subject was under-researched. Any weight loss regime will disrupt normal physiological mechanisms but additional concerns have to do with the environmental pollutants stored in fat tissue, pollutants like DDT and organochlorine. These can be released into the circulatory system as the fat is metabolized during weight loss. Once circulating in the body, hypothetically there could be adverse effects on fertility and pregnancy. “We don’t know how many calories are needed, how long women should diet, or whether they should do it at all during infertility treatment,” Legro said at the bi-annual Updates in Infertility Treatment meeting in Seville.
There have been a few studies of weight loss and pregnancy. Studies of low calorie diets which brought a weight loss of 8.8% of body weight over a six week period had to be stopped because research showed poor oocyte numbers, reduced fertilization, and low pregnancy rates for the women in the study. Women using IVF while on vigorous exercise programs also experience more implantation failure.
The real dilemma is whether the success rate is better for an obese woman without intervention or the woman who undergoes dramatic weight loss, for instance through bariatric surgery. Fertility is always better for the woman with the lower BMI, but studies are not present to support the best way to get there for fertility. Compliance with weight loss studies are particularly difficult with the majority of participants dropping out due to an inability to stay with the program. For overweight women every one unit of BMI over 29 equals a 4% decrease in their chance for successful pregnancy.
“Our current thoughts are that caloric restriction per se during preconception has harmful effects on ooctye competence. For this reason we don’t tell women to proceed with weight loss concurrently while undergoing infertility treatment,” Legro concluded. Still, more research is needed.
Source: Medical News Today, UIT2010
