2.3 Ovarian stimulation and oocyte retrieval
Ovarian stimulation began on the second day of menstruation, and all patients were given recombinant follicle stimulating hormone (r-FSH) (Gonal-F, Merck Serono, Switzerland) or urinary gonadotropins. The initial FSH dose is determined by the physician based on age, antral follicle count (AFC), basal FSH, estradiol (E