This prospective randomized placebo-controlled double blind clinical trial will conducted in Ain Shams University maternity Hospital including 120 women diagnosed with clomiphene citrate resistant polycystic ovary syndrome. After laparoscopic ovarian drilling, they will be randomized to either receiving 50 mg oral clomiphene citrate twice daily and oral NAC 1,200 mg/day for 5 days starting from cycle day 2 to cycle day 6 (group 1 = 60 patients) or clomiphene citrate only (group 2 = 60 patients). The primary outcome will be biochemical pregnancy rate, secondary outcomes include Clinical pregnancy rate, ovulation rate, live birth rate, number of follicles ≥ 18 mm and endometrial thickness at triggering ovulation, mid- luteal sub-endometrial blood flow indices, and incidence of side effects.

Inclusion Criteria:

• Body mass index (BMI) between 25 and 30 Kg/m 2.
• CC-resistant Polycystic ovary syndrome

Exclusion Criteria:

• • Patients with BMI under 25 or over 30 Kg/m 2.

  • Hyper or hypothyroidism, or hyperprolactinemia.

  • Current or previous (within the last six months) use of oral contraceptives, glucocorticoids, antiandrogens, antidiabetic and anti-obesity drugs or other hormonal drugs.

  • Intention to start a diet or a specific program of physical activity.

  • Organic pelvic diseases.

  • Tubal or male factor infertility.

  • Interval of earlier treatment with any of the fertility drugs of less than 6 months.

  • Contraindication to either:

    • Clomiphene citrate: liver disease, undiagnosed abnormal uterine bleeding, uterine fibroids, endometrial cancer, ovarian enlargement or hyper stimulation
    • HCG injection: ovarian enlargement or hyper stimulation