Letrozole, an aromatase inhibitor, has shown to be effective in inducing ovulation and pregnancies in women with anovulatory PCOS and in patients with CC resistance or failure.[13] It also improves the ovarian response to FSH in poor responders.[14] We had better results with letrozole as compared with CC [17.09% (115/673 cycles) vs 12.74% (85/667 cycles) respectively]. This evidence concerns the gene CYP19A1 and polycystic ovary syndrome.