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Joan Bengtson, M.D., is assistant professor of obstetrics, gynecology and reproductive biology at Harvard Medical School and a member of the Department of Obstetrics, Gynecology & Reproduction at Brigham and Women's Hospital.
Question:
Does weight determine fertility? I have three children; my youngest is 8 years old. I have gained more than 50 pounds since my last pregnancy, and have not gotten pregnant since. Could being overweight be a factor?
Answer:
Excess weight is one of many factors that affect fertility. Fertility refers to the capacity of a couple to conceive and have children. This is an enormously complex biological process, and one that can be influenced by many variables. Since so many factors are involved, it is often difficult to quantify the impact of any one thing in particular, but maternal weight is clearly important.
Body mass index (BMI) is a calculation that describes the relationship between weight and height. It is a good measure of body fat content. Women with a high body mass index are much more likely to have fertility problems compared with fit women. Excess body fat disrupts the monthly hormone cycle that directs the ovary to produce and release the egg.
Excessively low BMI is also associated with infertility. Women with very high and very low weights also have an increased risk of pregnancy complications when they do conceive. Preparing for pregnancy is an ideal time for women to address issues like weight control, both for fertility concerns and for their general well being and good health.