Association between body mass index and oocyte maturation in patients triggered with GnRH agonist who are at high risk for severe ovarian hyperstimulation syndrome: an observational cohort study

Research question: Is body-mass index (BMI) associated with oocyte maturation in women at high risk for developing severe ovarian hyperstimulation syndrome (OHSS) who are triggered with gonadotrophin releasing hormone (GnRH) agonist? Design: Prospective observational cohort study. A total of 113 patients at high risk for severe OHSS (presence of at least 19 follicles >= 11 mm) pre-treated with gonadotrophin releasing hormone (GnRH) antagonists and recombinant FSH were administered 0.2 mg triptorelin to trigger final oocyte maturation. Patients were classified in two groups depending on their BMI: BMI less than 25 kg/m(2) (n = 72) and BMI 25 kg/m(2) or over (n = 41). Baseline, ovarian stimulation and embryological characteristics, as well as luteal-phase hormone profiles, were compared in patients classified into the two BMI groups. The main outcome measure was the number of mature oocytes. Results: A significantly higher number of mature (metaphase II) oocytes (19 [18-21] versus 16 [13-20], P = 0.029) was present in women with BMI less than 25 kg/m(2) compared with those with BMI 25 kg/m(2) or greater. The number of retrieved oocytes, the number of fertilized oocytes, oocyte retrieval, maturation and fertilization rates were similar in the two groups. A significantly higher dose of recombinant FSH was required for patients with BMI 25 kg/m(2) or greater compared with patients with BMI less than 25 kg/m(2) (1875 [1650-2150] IU versus 1650 [1600-1750] IU, P = 0.003) and the two groups displayed different luteal phase hormonal profiles. Conclusions: Among women at high risk for developing severe OHSS who are triggered with a standard dose (0.2 mg) of the GnRH agonist triptorelin, women with BMI 25 kg/m(2) or greater had significantly fewer mature oocytes, required a higher total dose of recombinant FSH compared with women with BMI less than 25 kg/m(2).