Evaluation of The Effect of Letrozole in the Ovarian Hyperstimulation Syndrome Prevention in Participants at Risk of Treatment with Ovulation-Stimulating Drugs: A Randomized Controlled Trial

Background: This study aims to evaluate the effect of Letrozole (LE) in reducing ovarian hyperstimulation syndrome (OHSS) in high-risk participants with polycystic ovary syndrome (PCOS) treated with In vitro fertilization (IVF).   Methods: This study was a randomized clinical trial in which participants were randomly divided into two groups (n= 25 per group). Based on GnRH-antagonist protocol, recombinant follicle stimulating hormone 150 units/day subcutaneously and human menopausal gonadotropin 75 units/day intramuscularly used from day 2 of the menstrual cycle. In the study group, Letrozole 5 mg daily was added simultaneously with gonadotropin during the first five days of the IVF cycle and in the control group placebo was added.   Results: There were statistically significant differences among the groups in terms of Estradiol level on Trigger Day (p= 0.04). The total days of stimulation and cumulative Gonadotropin dose were significantly lower in the Letrozole group (p= 0.00). There were no significant differences between the groups in terms of the number of oocytes retrieved, numbers of implanted embryos, and clinical pregnancy rates (p-value 0.05). There was only one moderate case in the intervention group and 9 moderate symptoms in the control group (p= 0.04).   Conclusions:Administration of Letrozole with GnRH antagonist protocol, conventional protocol in PCOS cases in IVF cycle, had a significant effect on reducing the incidence of OHSS. So, if the future studies prove LE co-administration may lessen the incidence of OHSS, LE will be a highly potent drug for preventing OHSS in PCOS cases.