The inclusion criteria will be for IUI: women under 38 years old, tubal patency demonstrated by hysterosalpingography, normal uterine scan, normal basal hormonal levels, body mass index < 27 kg/m2, and absence of polycystic ovarian syndrome and endometriosis. For normal IVF cycles and oocyte donation cycles only first cycles will be analyzed. Cycles will be studied only in couples with absence of severe male factor.