Letrozole is a chemical compound, CGS 20267 which is a third-generation, nonsteroidal aromatase inhibitor.

Letrozole blocks estrogen synthesis by directly affecting the hypothalamic-pituitary-ovarian axis, subsequently, increases gonadotropins which increase pregnancy rates. Possible positive outcomes of aromatase inhibitors over selective estrogen-receptor modulators include a more physiologic hormonal stimulation of the endometrium which increases receptivity, a lower multiple-pregnancy through single follicle growth, a lesser side-effect especially vasomotor and mood symptoms, and more prompt clearance from blood, hence, reducing the probabilities of periconceptional exposure

The first pilot study for the clinical use of letrozole for ovarian induction in polycystic ovary syndrome (PCOS) patients was done in 2000.

In large randomized study, letrozole was superior to clomiphene as a treatment for anovulatory infertility in women with the polycystic ovary syndrome. Letrozole was also associated with higher live-birth and ovulation rates.

Ovulation induction with letrozole is associated with an ovulation rate of 70%-84% and a pregnancy rate of 20%-27% per cycle.

While in another study which Compare the Effect of Letrozole Alone with Letrozole Plus N-Acetylcysteine on Pregnancy Rate in Patients with Polycystic Ovarian Syndrome, the pregnancy rate was 7.5% in letrozole alone group .

Human chorionic gonadotropin (HCG) hormone will replace the naturally surging luteinizing hormone at mid-cycle, subsequently, will lead to full maturation of oocytes resulting in ovulation. Additionally, HCG will also enhance the endometrial quality by stimulating the corpus luteum. HCG is a hormone that is produced mainly by the placental syncytiotrophoblasts cells, it is also produced by other organs in minute amounts (Liver, colon and pituitary gland). HCG main function is maintaining pregnancy through stimulating the corpus luteum to produce progesterone.

This hormone is the cornerstone drug for inducing final maturation of follicles during a diversity of infertility treatment protocols.

In order to diagnose Polycystic ovarian syndrome two out of three Rotterdam criteria should be present. These criteria are: chronic anovulation, clinical and/or biochemical evidence of hyperandrogenism, and polycystic ovaries by ultrasound .

incidence of PCOS from 6% to 21% when the ESHRE/ASRM 2003 criteria were applied. Infertility (clinical definition) is currently defined as 1 year of unwanted non-conception with unprotected intercourse in the fertile phase of the menstrual cycles

Inclusion Criteria:

• Infertile women with PCOS
• Normal hysterosalpingography
• Normal semen analysis according to WHO parameters are major prerequisites

Exclusion Criteria:

• Infertile women with causes other than PCOS,
• Ages <18 or >35 years
• women taken confounding medications like other infertility drugs
• Insulin sensitizers or hormones
• Abnormal hysterosalpingography
• Subnormal semen analysis