Letrozole use during frozen embryo transfer cycles in women with polycystic ovary syndrome

Objective: To investigate whether live birth rate (LBR) following frozen-thawed embryo transfer in letrozole-stimulated cycles (L-FET) differs from LBR after artificial-cycle frozen-thawed embryos transfers (AC-FET) in women with polycystic ovary syndrome (PCOS). Design: Retrospective cohort study. Setting: Tertiary-care academic medical center. Patient(s): A total of 2,664 patients with PCOS who fulfilled the inclusion criteria were enrolled in the period from 2011 to 2016. Interventions(s): Letrozole use versus hormone replacement therapies during FET. Main Outcome Measure(s): LBR per embryo transfer was the primary outcome. The secondary end points included ongoing and clinical pregnancy rate, cancellation rate, endometrial thickness, and pregnancy loss rate. Multivariable logistic regression analysis was performed to adjust for potential confounders. Result(s): In our crude analysis, LBR per embryo transfer was similar between groups (54.4% in the L-FET vs. 50.7% for the AC-FET). The crude odds of pregnancy loss was significantly lower in L-FET compared with AC-FET (9.1% vs. 17%). Nonetheless, after adjusting for possible confounding factors, LBR was significantly higher in L-FET compared with AC-FET. Moreover, the rates of pregnancy loss remained consistently lower in the L-FET group than in the AC-FET group. Conclusion(s): In patients with PCOS undergoing FET, letrozole use for endometrial preparation was associated with higher LBR compared with artificial cycles, albeit after statistical adjustment for confounding factors. Future prospective randomized studies are needed to verify our findings. ((C) 2019 by American Society for Reproductive Medicine.)