Does obesity affect live birth rates with IVF?
Approximately 64% of American women are overweight or obese. The highest rate of obesity is in women 20 – 29 years old. Obesity is associated with an increase in heart disease, high blood pressure and diabetes. It can also negatively affect a woman’s fertility. Obese women often have irregular or absent menses and pregnancy rates are lower even in obese women with regular menses. Pregnancy complications are higher in obese women including high blood pressure, diabetes, bleeding after delivery, increased baby weight, difficult labor and increased chance of an operative delivery.
The Body Mass Index (BMI) is a commonly used metric to assess obesity. BMI is defined as weight in kilograms divided by the square of their height in meters (kg/m2). According to the most recent World Health Organization (WHO) classification, patients fall into following groups based on their BMI. Those with a BMI <18.50 kg/m2 (underweight), 18.50–24.99 kg/m2 (normal), 25.00–29.99 kg/m2 (overweight), 30.00–34.99 kg/m2 (obese class I), 35.00–39.99 kg/m2 (obese class II), and >40.00 kg/m2 (obese class III).
In a recent paper published in Fertility and Sterility, Moragianni et al. (Fertil Steril 2012;98:102-8) from Boston IVF evaluated the affect of BMI on live birth rates in 4,609 patients undergoing their first IVF cycle. This is a large group of patients from a single institution and their findings are interesting.
- Patients with a BMI > 30 kg/m2 had significantly decreased odds of implantation, clinical pregnancy and live birth.
- Compared with normal BMI, the adjusted odds of live birth are decreased by 37% in class I obesity, 61% in class II obesity, and 68% in class III obesity.
- Obese patients required higher daily doses of fertility drugs, and had lower peak estradiol levels.
- The chances of cycle cancellation, spontaneous miscarriage, ectopic pregnancy or multiple births were not significantly different.
The authors suggest that their data can be used when counseling and educating patients regarding the beneficial lifestyle changes and weight loss required to optimize the success of their IVF treatment.