The purpose of this study is to evaluate the effect of concomitant administration of estradiol during use of clomiphene citrate (CC) for induction of ovulation in infertile women.

Women will be randomly divided into two groups; CC-E2 group and CC group. Women in the CC-E2 group will receive CC (100 mg/day for 5 consecutive days from day 2 of cycle) and estradiol (2 mg/day for 5 consecutive days from day 2 of cycle). Women in the CC group will receive CC (100 mg/day for 5 consecutive days from day 2 of cycle) and placebo mimic estradiol (for 5 consecutive days from day 2 of cycle). Transvaginal sonography (TVS) scan will be performed regularly for monitoring of follicular growth (folliculometry); starting from day 10 of the stimulation cycle and repeated every 2-3 days. When there will be at least one follicle ≥ 18 mm in diameter, final oocyte maturation will be induced by intramuscular administration of 10000 IU of human chorionic gonadotropin (HCG) and timed intercourse will be advised. If there will be no follicle ≥ 12 mm by day 16 of the cycle, monitoring of follicular growth will be discontinued and the cycle will be presumed to be anovulatory. Ovulation will be documented by TVS scan one week after triggering of oocyte maturation and will be confirmed by assessing the midluteal serum progesterone level. Each woman will be subjected to ovarian stimulation for a maximum of 3 consecutive cycles except if she gets pregnant in the first or second cycle.

Inclusion Criteria:

• Infertile women with eugonadotrophic anovulation/oligoovulation.
• Unexplained infertility.

Exclusion Criteria:

• Age < 20 or > 35 years.
• Body mass index (BMI) < 18.5 kg/m2 or > 25 kg/m2.
• Presence of any infertility factor other than anovulation/oligoovulation.
• Previous history of ovarian surgery or surgical removal of one ovary.
• Previous exposure to cytotoxic drugs or pelvic irradiation.
• Metabolic or hormonal abnormalities.