['To compare subcutaneous (SC) and intramuscular (IM) hCG administration and their association with body mass index (BMI) in women undergoing IVF-ET using hMG and ICSI.', 'Prospective, randomized controlled trial.', 'Private infertility clinic.', 'Twenty-one ovulatory women, 29-39 years, were enrolled. Treatment of one patient who failed to respond to hMG was canceled.', 'A standard IVF-ET treatment plan using an initial dose of 300 U of hMG was followed. Patients were randomly assigned to receive 10,000 IU hCG, either IM in the gluteal region or SC in the lower abdomen. Exactly 12 hours later, serum for hCG determination was obtained. All oocytes were fertilized using ICSI technology.', 'Human chorionic gonadotropin levels 12 hours after injection, BMI, and oocyte maturity.', 'No significant differences in hCG levels were found, with mean levels of 225 +/- 24 mIU/mL for SC injection versus 213 +/- 26 mIU/mL for IM injection. No differences were observed in the percentage of mature oocytes. A significant negative correlation was found between BMI and hCG levels in all patients, regardless of route of administration.'] Are serum human chorionic gonadotropin levels correlated with body mass index rather than route of administration in women undergoing in vitro fertilization -- embryo transfer using human menopausal gonadotropin and intracytoplasmic sperm injection?