Women, Weight and Fertility

According to recent studies, obesity is clearly linked with a longer time to conception. Having a body mass index less than 18 or over 32 is associated with problems ovulating and conceiving, as well as problems during pregnancy. A woman’s weight can affect her fertility. We know that at both extremes, very thin and obese, that there can be disruption of the normal process of regular, consistent ovulation.  A high or a low Body Mass Index (BMI) can lead to anovulation. The good news is that a change in diet for a short period of time, and even some medications, can help these women in an attempt to become pregnant.

Body mass index is calculated by weight (kilos) divided by height (meters) squared. To convert from pounds to kilos, take the weight in pounds and divide it by 2.2, and to convert from inches to meters, take the height in inches times 0.0254. A standard medical definition of “normal” body weight is a BMI of about 18.5 – 24.9.  A BMI under 18.5 indicates that the person is “underweight” and a BMI of 25.0 – 29.9 indicates that the individual is “overweight”, but not obese.  A BMI over 30 indicates obesity.

Obesity is associated with increased risk for several serious diseases. Some recently published studies have shown a relationship between BMI and IVF (In Vitro Fertilization) success rates. If you are overweight or obese (BMI over about 30) and having trouble getting pregnant, try to lose weight. If you have irregular menstrual cycles (anovulation, or irregular ovulation) and you are overweight, weight loss might make your cycle regular – thereby making you more fertile.

Bottom Line: If you are obese and having trouble getting pregnant, or need IVF, you might have a significantly improved chance for success if you reduce your weight before going through the procedure. If you have a low BMI and cannot get pregnant, you may want to gain some weight. Consult with your health care provider or fertility specialist when planning on making changes with your weight. For more questions about weight, reproductive health, trying to conceive and IVF, contact your MD, OB-GYN or RE (Reproductive Endocrinologist / Fertility Doctor), and consider getting additional support and care via a nutritionist or health care provider who is trained in adjunctive reproductive health care.