The influence of body mass index on in vitro fertilization outcome.

Objective: To examine whether body mass index (BMI) influences the outcome of in vitro fertilization (IVF).

Methods: We studied 516 IVF cycles, 438 undergone by nonobese (BMI < or = 30) and 78 by obese (BMI > 30) women who all had an a priori favorable prognosis (age < 40 years and first, second, or third IVF cycle).

Results: Pregnancy was achieved in 122 (27.9%) nonobese and 12 (15.4%) obese women. The obese women required significantly longer stimulation and more gonadotropin ampoules, and had lower peak estradiol levels and a significantly lower fertilization rate; obese poor responders had a significantly lower pregnancy rate than nonobese poor responders; and the prevalence of poor responders was significantly higher among obese than nonobese women (28.2% vs 16.9%, P < 0.04).

Conclusion: While the likelihood of poor responders was increased among obese women, reasonable conception rates were achieved in nonobese poor responders, and were comparable to the rates in nonobese and obese normal responders.