Pregnancy outcomes after frozen-thawed embryo transfer using letrozole ovulation induction, natural, or programmed cycles

Objective: To evaluate and compare pregnancy outcomes between letrozole ovulation induction, natural, and programmed frozen -thawed embryo transfer (FET) cycles in a population based in the United States.Design: Retrospective cohort study.Setting: Single university-affiliated infertility practice.Patient(s): A total of 3,148 FET cycles consisting of patients aged %45 years transferring blastocysts that were created from autolo-gous oocytes between January 2015 and July 2021.Intervention(s): None.Main Outcome Measure(s): The primary outcome was the ongoing pregnancy rate (OPR) or live birth rate (LBR). The secondary out-comes included clinical pregnancy and clinical loss rates (CLRs). Result(s): The OPR/LBR was higher among letrozole FETs than among programmed FETs (adjusted risk ratio [aRR] 1.11, 95% confi- dence interval [CI] 1.02-1.21) but comparable to natural FETs (aRR 1.05, 95% CI 0.96-1.14). The OPR/LBR was comparable between natural and programmed FETs (aRR 1.06, 95% CI 0.99-1.13). The CLR was lower in the natural FET group than in the programmed FET group (aRR 0.62, 95% CI 0.46-0.84). There were no differences in CLRs between letrozole and programmed FETs and between le-trozole and natural FETs. Among ovulatory women, the OPR/LBR among letrozole FETs was higher than that among programmed FETs (aRR 1.16, 95% CI 1.05-1.28). The CLR among ovulatory women was significantly lower in both letrozole FETs (aRR 0.44, 95% CI 0.22- 0.87) and natural FETs (aRR 0.59, 95% CI 0.43-0.80) than in programmed FETs. Among anovulatory women, the OPR/LBR in the le-trozole FET group was similar to that in the programmed FET group (aRR 0.95, 95% CI 0.79-1.13).Conclusion(s): Letrozole and natural FET clinical outcomes were improved compared with programmed FET outcomes. (Fertil Sterile 2022;118:690-8. (c) 2022 by American Society for Reproductive Medicine.)El resumen esta disponible en Espanol al final del articulo.

Automated summary

This retrospective cohort study compared the pregnancy outcomes of letrozole ovulation induction, natural cycles, and programmed frozen-thawed embryo transfer (FET) cycles. The results showed that the ongoing pregnancy rate/live birth rate was higher in letrozole FETs than in programmed FETs, but comparable to natural FETs. The ongoing pregnancy rate/live birth rate was comparable between natural and programmed FETs. The clinical loss rate was lower in the natural FET group than in the programmed FET group.