P-644 Effect of Letrozole co-stimulation with gonadotropin in women with normal ovarian reserve on oocyte maturation: a Randomized controlled trial

Abstract

Abstract Study question To define whether letrozole co-stimulation with gonadotropin in normal-ovarian reserve women will improve the number of oocyte maturation. Summary answer Letrozole co-stimulation in normal ovarian reserve resulted in a reduced number of MII. What is known already Letrozole functions as an aromatase inhibitor. By inhibiting this enzyme, letrozole effectively lowers estrogen levels. Thus, letrozole prevents the estrogen-negative feedback to the HPO axis, which can increase the secretion of gonadotropins from the pituitary gland to promote folliculogenesis. The application of letrozole co-stimulation in women with a normal ovarian reserve is still debated. Study design, size, duration This study is an open-labeled, randomized controlled trial. Letrozole co-stimulation with gonadotropin in women with normal ovarian reserve. The RCT was conducted at the Fertility and Reproductive Biology Unit, Department of Obstetrics and Gynecology, Faculty of Medicine, Siriraj Hospital in Thailand, from March 2023 to October 2023. Participants/materials, setting, methods One hundred forty-four infertile women 18-40 years old with normal ovarian reserve (AMH 1.2-7 ng/ml, AFC ≥ 5) were random to gonadotropin co-stimulation with letrozole 5 mg once daily (n = 72) and gonadotropin alone (n = 72). The number of MII oocytes, follicle-to-oocyte index, GDF-9 and BMP-15 in follicular fluid were assessed. Main results and the role of chance Letrozole co-stimulation resulted in a significantly reduced number of MII [8 (4,12) vs 9 (5, 15.8), p = 0.042] and the rate of MII [ 71.7(60, 83.8) vs 80 (66.7, 90), p = 0.013]. However, the number of retrieved oocytes [12 (6,16.8) vs. 12 (6,16), p = 0.335] and FOI [85.7 (57.4,107.5) vs 84.2 [61.8, 112.5], p = 0.396] remained unchanged. The total dose of gonadotropin in the letrozole group was no different from the control group [1,350 (1,200, 1,650) vs 1,500 (1,350, 1,718.8) I.U., p = 0.137]. The duration of ovarian stimulation was shortened in the letrozole group compared to the control group [9 (8, 10) vs 9 (8.3, 10) days, p = 0.027]. The letrozole and control group had a similar level of GDF-9 (0.036 ± 0.003 A.U. vs. 0.028 ± 0.004 A.U., p = 0.119, letrozole and control group, respectively) and BMP-15 (0.034 ± 0.002 A.U. vs. 0.033 ± 0.004 A.U., p = 0.923, letrozole and control group respectively) in follicular fluid. Limitations, reasons for caution This study was open-label, with limited generalizability due to 91% of ovarian stimulation being strict to the research protocol (r-FSH and antagonist protocol) and no pregnancy outcome. Wider implications of the findings The study showed no benefit of letrozole co-stimulation in women with normal ovarian reserve. Trial registration number TCTR20221125002