How Fat Can Affect Fertility

by Jennifer Redmond for FertilityAuthority

According to a recent study of 323 women, being obese or overweight doubles a woman’s risk of miscarriage following in vitro fertilization, or IVF.

Dr. Joseph Hill, a fertility doctor at Fertility Centers of New England, in Reading, MA, says he’s not surprised--these findings correlate to what he and others have seen in their infertility practices. According to Hill, both implantation (pregnancy) and live birth rates are lower in overweight women, “most likely due to an increase in estrogens and in male hormones.” Estrogen is produced by the ovaries, as well as by fat tissue, therefore higher levels of estrogen are found in women who are overweight. The ovaries also produce small amounts of the male hormone testosterone. When a woman has high levels of testosterone, she may be prone to infertility. (Women with PCOS have higher levels of testosterone.)

Body Mass Index and Fertility

Body mass index (BMI) is a measure of body fat based on a calculation of height and weight.

* BMI of less than 18.5 – Underweight
* BMI 18.5-24.9 – Normal weight
* BMI 25-29.9 – Overweight
* BMI 30 and greater – Obese

For every five BMI points over 30, your chance of pregnancy decreases. Here’s how Hill breaks it down:

* Women with a BMI of 30-34 have a five percent lower chance of pregnancy than women with a BMI less than 30.
* Women with a BMI of 35-39 have a 15-20 percent lower chance of pregnancy than women with a BMI less than 30.

Hill says he does not treat women with a BMI greater than 40, as their chance of success is negligible.

Calculate Your BMI

Use this formula to calculate your BMI:

1. Multiply your weight (in pounds) by 703
2. Divide that total by your height (in inches)
3. Divide the total again by your height (in inches)

Healthy Lifestyle Changes

Hill recommends that his overweight patients enter a weight management program. The combination of healthy lifestyle changes – including diet and exercise - and support is often a winning formula for women trying to achieve a weight loss goal.