• Anovulation;
  • body weight;
  • infertility;
  • obesity;
  • ovulation induction;
  • polycystic ovary syndrome

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.