The influence of body weight on response to ovulation induction with gonadotrophins in 335 women with World Health Organization group II anovulatory infertility.

OBJECTIVE: To assess the influence of body weight on the outcome of ovulation induction in women with World Health Organization (WHO) group II anovulatory infertility. DESIGN: The combined results of two studies in which either a highly purified urinary follicle-stimulating hormone or highly purified urinary menotrophin were compared with recombinant follicle-stimulating hormone. SETTING: Thirty-six fertility clinics. POPULATION: A total of 335 women with WHO group II anovulatory infertility failing to ovulate or conceive on clomifene citrate. METHODS: Ovarian stimulation using a low-dose step-up protocol. MAIN OUTCOME MEASURES: The effects of body weight on ovarian response, ovulation rate and pregnancy rate after one treatment cycle. RESULTS: With increasing body mass index (BMI), a higher threshold dose of gonadotrophins was required and there were more days of stimulation; yet, despite a greater concentration of antral follicles, there were fewer intermediate and large follicles. There was no difference in the rates of ovulation and clinical pregnancy in relation to body weight. CONCLUSIONS: Body weight affects gonadotrophin requirements but not overall outcome of ovulation induction in women with anovulatory polycystic ovary syndrome and a BMI of less than 35 kg/m2.