Letrozole Versus Clomiphene Citrate for Ovulation Induction in Women With Poly Cystic Ovary Syndrome ( PCOS )

110 infertile women diagnosed as polycystic ovary syndrome (PCOS) at the age group of 20-35 distributed randomly : * 55 women will receive letrozole 2.5mg twice daily orally from the 2nd day to the 6thday of the cycle for three successive cycles. * 55 women will receive clomiphene citrate 50 mg twice daily orally from the 2nd day to the 6thday of the cycle for three successive cycles. Patients will be subjected to: Complete history taking: 1. Details about name, age 2. Menstrual history with determination of menarche 3. Amenorrhea or oligomenorrhea , Regularity of the cycle 4. History of endocrine disease. 5. History of previous operations. * Physical examination: * General examination: With special concern to: --Acne. --Hirsutism . --Weight. --Height --BMI was determined : Wt. in kg ـــــــــــــــــــ = ) Height in m)2 \- Abdominal examination : * for scar of previous pelvic or abdominal operations . * Pelvic examination : * vaginal examination for enlarged cystic ovaries. * ultrasound for diagnosis of pcos. PARAMETERS: (1) rate of ovulation (primary parameter). (2) serum progesterone level on day 21. (3) number of mature follicles produced per cycle. (4) mean endometrial thickness. (6) chemical pregnancy. (7) ongoing pregnancy