Women underwent controlled ovarian hyperstimulation with a GnRH short antagonist (cetrorelix; Merck Serono, Geneve, Switzerland; ganirelix; Organon, Oss, the Netherlands) protocol in the majority of the cases. For stimulation, rFSH was mainly used (Puregon; Organon; Gonal-F; Merck Serono, Germany). About 36 h before oocyte recovery, HCG was administered (Pregnyl; Organon). Estradiol serum levels were assayed at the day of HCG or 1 day before.28 (link)29 (link)