Ovarian stimulation
Women started their IVF with ovarian stimulation using either PPOS or antagonist protocols. For the PPOS protocol, on Day 2-3 of the menstrual cycle, human menopausal gonadotrophin (hMG) (Lebaode, Lizhu, China) or recombinant FSH (Puregon, Organon, Dublin, Ireland or Gonal F, Merck Serono S.p.A, Modugno, Italy) was given at 150–225 IU per day based on the AFC count, age of women and previous ovarian response, according to the standard operating procedures of the centre. Medroxyprogesterone MPA (MPA, 10 mg/d, Shanghai Xinyi Pharmaceutical Co., China) was also given on the same day afterwards. Ovarian response was monitored by serial transvaginal scanning with or without hormonal monitoring. Further dosage adjustments were based on the ovarian response at the discretion of the clinicians in charge. For the antagonist protocol, antagonist 0.25mg daily (Orgalutran, Organon, Dublin, Ireland) was given from the 6th day of ovarian stimulation until the day of ovulation trigger.
When three leading follicles reached ≥18 mm in diameter, triptorelin (0.1 mg; Decapeptyl, Ferring Pharmaceuticals, Netherlands) and hCG (2000 IU; Lizhu Pharmaceutical Trading Co., China) or Ovidrel 250 microgram (Merck Serono S.p.A., Modugno, Italy) were given to trigger final maturation of oocytes. Oocyte retrieval was performed around 36 hours later.