Baseline patient characteristics.

The study investigates whether a 3-day pretreatment course with a GnRH antagonist in the early follicular phase has an impact on the number of retrieved COCs in a GnRH antagonist stimulation protocol. This is a retrospective single center crossover study involving women who did not conceive after one GnRH antagonist stimulation cycle (“standard cycle”) and proceeded with another GnRH antagonist stimulation cycle preceded by early administration of GnRH antagonist for 3 days (“pretreatment cycle”) with fresh embryo transfer or frozen embryo transfer. 430 patients undergoing 860 cycles were included. The mean female age was 34.4 ± 4.8 years. Indications for fertility treatment included unexplained infertility (34.3%), male-factor infertility (33.3%), age (16.9%), PCOS (8.2%), tubal (4.7) and endometriosis (2.6%). All cycles were divided into two groups: group 1 (standard, 430 cycles) and group 2 (pretreatment, 430 cycles). The mean duration of stimulation was similar in both groups (10.3 vs 10.3 days, p = 0.28). The starting dose of gonadotropin (234.9 vs 196.8 IU, p