Figure 1. Schematic representation of the assessments in spontaneous and stimulated cycles. Following a spontaneous cycle, all 22 participants underwent a stimulated cycle using 100 mg/day of clomiphene citrate between days 3 and 7 of the cycle. When the leading follicle had a diameter of 17 mm (represented by **), they received 10.000 UI of human chorionic gonadotrophin (hCG) for final oocyte maturation. Endometrial biopsy (EB) was performed 5 days after ovulation confirmation (represented by *) by ultrasonography. In both cycles blood samples (BS) were taken at the early proliferative phase (days 1 -3), in the midproliferative phase (days 8-10), when confirmed ovulation, and five days after ovulation.