Expert answers: Does weight affect fertility or pregnancy?

Written by Meera Shah, M.B., Ch.B., a Mayo Clinic endocrinologist

It is estimated that approximately 30 percent of women of childbearing age in the USA are in the obese BMI category. Obesity is a risk factor for several complications during pregnancy, including the development of high blood pressure and diabetes in the mother and developmental abnormalities in the fetus. Maternal obesity may also contribute to a more difficult labor and delivery and independently increases the risk for cesarean delivery.

Obesity can also adversely affect fertility and the chance of spontaneous conception. Women who are overweight or obese may have irregular menstrual cycles and other health problems that may make it more difficult to become pregnant. In men, being obese may lower overall sperm quality.

How weight loss can help

Research studies have primarily focused on women diagnosed with infertility. Weight loss in overweight or obese women attempting to become pregnant has been shown to increase the rate of spontaneous conception and to decrease the need for additional fertility treatment.

Weight loss options when trying to become pregnant

All modalities of weight loss may be considered to help achieve meaningful results.

Women who participate in intensive lifestyle modification alone can achieve adequate weight loss over a period of time. In women who are actively trying to become pregnant, current FDA-approved weight loss drugs are contraindicated because of the risk of fetal birth defects. However, women who are willing to defer pregnancy and use contraception while using a weight loss drug may achieve greater weight loss thus increasing the chance of spontaneous conception and potentially avoiding the need for fertility treatment.

Bariatric surgery is an effective weight loss tool that has also been shown to increase pregnancy rates in women diagnosed with infertility. However, while pregnancy after bariatric surgery is generally safer than pregnancy at a higher weight, women should be aware of nutritional factors, and other unique risks associated with pregnancy following bariatric surgery. Women are also advised to defer pregnancy for at least 12 months following bariatric surgery, which may be especially relevant to women who are already of advanced maternal age.

In summary, weight loss improves fertility and the chance of spontaneous conception in obese women who attempt to become pregnant. There are many options to help women lose weight. These are best discussed with your healthcare provider to find the right one for you.