RESUMEN
To compare the effect of letrozole to combined clomiphene citrate plus metformin as a first-line treatment to induce ovulation in women with polycystic ovarian syndrome [PCO]. In the present prospective randomised trial, 200 infertile women with PCOS were equally randomised to receive letrozole 2.5 mg for ,five days [days 3-7 of the cycle] or clomiphene citrate [CC]100 mg for five days [days 3-7 of the cycle] plus metformin 1500 mg daily for three treatment cycles. Human chroinic gonadotropine injection [HCG] was given when at least one follicle 18 mm present. The 3-month rate of ovulation, pregnancy and abortion were evaluated. The groups were similar with regard the baseline clinical characteristics and hormonal profiles. The ovulation rate was higher in the letrozole group [76.5% versus 71.6%] but without significant difference and the endometrial thickness at day of HCG was significantly higher in the letrozole group [8.6 mm versus 7.4 mm]. Letrozole shows higher pregnancy rate [45.7% versus 39.2%] and lower rate of abortion [10.8% versus 18.2%] but with no significance. The rate of multiple pregnancy was significantly higher in the CC metformin group 12.1% versus no case in the letrozole group letrozole is a suitable alternative first-line ovulation inducing drug in PCO