The effects of letrozole on women with endometriosis undergoing ovarian stimulation for in vitro fertilization.

This study aimed to analyze the effects of a new protocol with letrozole on the outcomes of in vitro fertilization (IVF) cycles in women with endometriosis. This retrospective cohort study was conducted for women diagnosed with endometriosis undergoing IVF from an infertility clinic. A new protocol, combination therapy with letrozole and gonadotropin, was used from August 2016 to January 2018 ('protocol 1', n = 38). From March 2014 to July 2016, conventional IVF with gonadotropin was administered ('protocol 2', n = 26). Age and ovarian reserve were comparable between the two groups. The patients who received protocol 1 resulted in a significantly lower peak estradiol level in IVF compared with those received protocol 2 (722 ± 1076 pg/mL versus 2168 ± 1521 pg/mL, p < .001). The length of stimulation, the total dose of gonadotropin, number of oocytes retrieved, fertilization rates, and number of embryos obtained were similar between the two groups. The mean percentage of mature oocytes was lower (69.9 ± 23.7% versus 80.2 ± 21.0%, p = .029) in patients with protocol 1. While maintaining low estrogen levels, the combination therapy with letrozole and gonadotropin produce similar oocyte and embryo yield to the conventional IVF protocol in women with endometriosis.