A comparison of the effects and pregnancy outcome of letrozole versus clomiphene citrate for ovulation induction in women with polycystic ovarian syndrome

Objective:To search for a new drug for ovulation induction through a comparison of the effects and pregnancy outcome of letrozole(LE)versus clomiphene citrate(CC)for induction of ovulation.Methods:The patients with polycystic ovarian syndrome(PCOS)undergoing ovarian stimulation were divided into LE group and CC group.All subjects received either LE at a dosage of 5.0mg daily from cycle day 3 to 7 plus HMG injection staring on day 7 or CC(100mg/day)from day 5 to day 9 plus HMG injection on day 6 until the day of HCG.The number of follicle ≥14 mm and follicle ≥16 mm,endometrial thickenss and pattern were observed on the day of HCG.Some samples were analyzed including serum E2,testosterone and LH on the day of HCG and E2 and P on day +7 after follicular rupture.Meanwhile,pregnancy rate were recorded as well as the case of miscarriage,ectopic and ovarian hyperstimulation syndrome(OHSS).Results:Despite there being significantly(P0.01)lower E2 level in the letrozole group,no significant differences between two groups were found in terms of endometrial thickenss and endometrial pattern on the day of HCG.However,endometrial thickenss was thinner 7 mm in 13 patients from the CC group at the time of HCG administration,without anyone in the LE group.Compared with the CC group,letrozole was associated with a statistically significantly fewer follicles ≥14 mm and no one patient with OHSS.The pregnancy rate and ongoing pregnancy rate were higher in the LE group,but a marked difference wasn't found between the two groups.Conclusion:Letrozole results in stimulation of ovarian folliculogenesis and the pregnancy rate similar to that seen with CC.