TUESDAY, July 9, 2013 (HealthDay News) -- Obese women who receive donated eggs for in vitro fertilization (IVF) are less likely than women of normal weight to have a successful pregnancy.
That's the finding of a study that reviewed more than 9,500 egg donations at three infertility clinics in Spain between 2000 and 2011. All of the egg donors were of normal weight, but the recipients ranged from lean to obese.
"Based on our results, the chance of having a baby by egg donation is reduced by around one-third for obese women," said Dr. Jose Bellver, of the Valencia Infertility Institute in Valencia, Spain.
The researchers compared the body-mass index (a measurement of body fat based on height and weight) of the egg recipients with their IVF results. As BMI increased, there were significant reductions in the rates of embryo implantation in the uterus, pregnancy, twin pregnancy and live birth.
For example, the live-birth rate was 38.6 percent in lean women, 37.9 percent in normal-weight women, 34.9 percent in overweight women and 27.7 percent in obese women. The rate of embryo implantation in the uterus was 40.4 percent in lean women, 39.9 percent in normal-weight women, 38.5 percent in overweight women and 30.9 percent in obese women.
These trends translated to a 27 percent lower chance of live birth for an obese woman than for a normal-weight woman, the researchers said. Their findings were scheduled for presentation Tuesday at the annual meeting of the European Society of Human Reproduction and Embryology in London.
"We found that obese recipients of eggs from normal-weight donors had a 23 percent lower implantation rate than normal-weight recipients, 19 percent lower clinical pregnancy rate and 27 percent lower live-birth rate," Bellver said in a society news release.
Overweight and obese women should be advised to shed excess pounds before trying to conceive through ovum donation or any other means, the researchers said. "The clinical evidence is now strong enough for implementing preconceptional health policies for obese patients considering assisted reproduction," Bellver said.
Although the study found an association between an IVF recipient's weight and the success of her pregnancy, it did not necessarily show a cause-and-effect link. Data and conclusions presented at meetings should be considered preliminary until published in a peer-reviewed medical journal.
The U.S. National Institute of Child Health and Human Development has more about assisted reproductive technology.