Inclusion criteria were as follows: women of good physical and mental health, under 37 years old, with regular menstrual cycles of 25-35 days, normal basal FSH and luteinizing hormone (LH) levels, body mass index (BMI) less than 30 kg/m2, presence of both ovaries and intact uterus, absence of polycystic ovaries, endometriosis, or gynaecological / medical disorders and a negative result in a screening for sexually transmitted diseases.