Luteal-phase support was provided using progesterone gel (Crinone 8% 90 mg, twice a day; Merck Serono) and estradiol per os (Valiera 2mg, twice a day; Laboratorios Recalcine). Serum hCG was measured 16 days after oocyte retrieval, and if positive, an ultrasound scan was performed at gestational weeks 7 and 12.