Ovarian stimulation, oocyte retrieval, denudation, ICSI and embryo culture

COH was performed with the GnRH antagonist protocol. Recombinant FSH (150–300 IU, Gonal-F; Serono) and/or hMG (75–150) IU; (Merional; IBSA) was administered on day 2 of the menstrual period. Starting on the sixth day of controlled ovarian stimulation, the ovarian response was monitored by serial transvaginal ultrasound (TV-USG) and by measuring serum E₂ and P₄ levels. When the leading follicle exceeded 13 mm in diameter, 0.25 mg of GnRH antagonist (Cetrotide; Serono) was started daily until the day of the last trigger. When at least two follicles reached 18 mm in diameter, patients were administered 250 μg of human chorionic gonadotropin (hCG; Ovitrelle, Serono) or 0.2 mg of triptorelin (Gonapeptyl, Ferring), and oocyte retrieval was scheduled 35 hours after the trigger administration [16].

The oocyte retrieval, denudation, and ICSI procedures were performed as described previously by Serdarogullari et al. [17]. ICSI was the fertilization method in all of the cycles included in this study. After microinjection, oocytes were cultured individually in a special pre-equilibrated culture dish. In our study, single-step media, namely, Continuous Single Culture Complete (CSCM-C) with Human Serum Albumin (Irvine Scientific) was used for embryo culture throughout the culture period.