The impact of obesity on female fertility has been widely studied, with much of the research finding an adverse effect on outcome. Most studies have pointed to excess weight causing issues with cycle regularity and ovulation. Now, a new study of nearly 10,000 patients found that obesity has effects on fertility beyond ovulation; it also reduces the receptivity of the uterus to embryo implantation, leading ultimately to fewer live births.
The study looked at women who underwent in vitro fertilization (IVF) with egg donation in Spain from 2000-2011. All of the egg donors were of normal weight, so their body weight could not affect the results. The recipients were of varying body weights: 15% were underweight with Body Mass Index (BMI) below 20, 60% were of normal weight with BMI 20-24.9, 18% were overweight with BMI 25-29.9 and the remaining 7% were obese with BMI of 30 or greater. By analyzing treatment outcomes by BMI group, researchers found that the rates of embryo implantation, pregnancy, twin pregnancy and live birth all significantly declined as BMI increased. Specifically, obese recipients had a 23% lower implantation rate than normal weight recipients, 19% lower clinical pregnancy rate, and 27% lower live birth rate.
The findings indicate that impaired endometrial receptivity may contribute to the decline in fertility in obese women, in addition to diminished egg and embryo quality. Study author, Dr. Jose Bellver of the Instituto Valenciano de Infertilidad concluded, “Based on our results, the chance of having a baby by egg donation is reduced by around one third for obese women.” The findings highlight the importance for overweight and obese women to get their weight under control prior to trying to conceive.
“Our favorite weight gain is from pregnancy!” Dr. Terry Simpson, expert weight loss surgeon in Arizona, told us. “Making a difference in by allowing previously infertile women become pregnant is one of the high points of weight loss surgery,” he said. A prior study presented at The Obesity Society’s scientific meeting in 2012 showed that when obese moms have bariatric surgery, there are benefits that can pass to her future children. You can read about that presentation here.
Related Reading: Large Study Finds Possibility of Safe Weight Loss During Pregnancy
Weight Loss Studies & Clinical