The effect of letrozole as an adjunct in GnRH-antagonist protocol on IVF/ICSI outcome in women with endometriosis: a randomized clinical trial

Background To evaluate the effect of adding letrozole to the antagonist ovarian stimulation protocol (COS) on in-vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) outcome in endometriosis patients. Methods This randomized clinical trial was carried out in the department of infertility treatment at Arash Women’s Hospital from May 2019 to May 2021. The eligible women with normal ovarian reserve tests who had endometriosis diagnosis and underwent IVF/ICSI cycles were evaluated. A flexible regimen of GnRH-antagonist protocol was used for COS. In the experimental ( n = 34), the patients received 5 mg letrozole daily for the first 5 days in combination with 150 IU of recombinant follicle-stimulating hormone (rFSH). In the control group ( n = 30), the patients received only the same dose of rFSH. The treatment cycle was compared between groups. Results Analysis of demographic characteristics, severity of endometriosis, and baseline hormonal tests of patients showed that the two groups were similar and comparable. The means of total used gonadotropins ampoules and serum E 2 level on oocyte trigger day in the letrozole group were significantly lower than those of in the control group ( P = 0.03 and P = 0.004, respectively). No statistically significant difference in terms of the total number of retrieved and MII oocytes as well as the total numbers of obtained and top-quality embryos, and cryopreserved embryos was found. Conclusion The co-treatment of letrozole with gonadotropins during the antagonist protocol was associated with a reduction in the total dose of gonadotropins, although it had no effect on the oocyte or embryo yield in patients with endometriosis. Trial registration The study was registered in the Iranian Registry of Clinical Trials on 2018 -07-13 (IRCT20150310021420N4 at www.irct.ir , registered while recruiting).