Obese women have alterations in their ovaries which might be responsible for an egg's inability to make an embryo, according to a new study accepted for publication in The Endocrine Society's Journal of Clinical Endocrinology & Metabolism (JCEM).
Obese women trying to become pregnant experience longer times to conception, even if they are young and have a regular menstrual cycle. This study sought to determine if there are alterations in an egg's environment in obese women which contribute to poorer reproductive outcomes.
"Characteristics of eggs are influenced by the environment in which they develop within the ovary," said Dr. Rebecca Robker, PhD, of Adelaide University in Australia and lead author of the study. "Our study found that obese women have abnormally high levels of fats and inflammation in the fluid surrounding their eggs which can impact an egg's developmental potential."
According to Dr. Robker, the fats might alter the very sensitive metabolism of the egg and such changes are known to be harmful to embryo formation. In addition, inflammation can damage cells and when this happens to eggs it can affect embryo survival.
For this study, researchers followed 96 women seeking assisted reproduction at a private clinic in South Australia from February 2006 to April 2007. Dr. Robker and her colleagues measured hormone and metabolite levels in follicular fluid obtained from the subjects' ovaries during their egg collection procedures. They found that obese women exhibited an altered ovarian follicular environment, particularly increased metabolite and androgen activity levels, which may be associated with poorer reproductive outcomes.
"Obesity is well known to cause changes in blood lipids and heightened inflammation which detrimentally affects a person's general health," said Dr. Robker. "Our research shows that obesity similarly changes the environment in the ovary which bathes and nourishes a woman's developing eggs."
Other researchers working on the study include Lisa Akison, Brenton Bennett, Penny Thrupp, Lindsay Chura, Darryl Russell, Michelle Lane and Robert Norman of the University of Adelaide in Australia.
The article "Obese Women Exhibit Differences in Ovarian Metabolites, Hormones and Gene Expression Compared to Moderate Weight Women," will appear in the May 2009 issue of JCEM.