Letrozole versus HRT in frozen-thawed embryo transfer cycles

Background: A progressive increase in FET cycles was observed in recent years. Different endometrial preparation strategies have been described, however, there is still some controversy as to the ideal endometrial preparation protocol.
Objective: To evaluate the efficacy of letrozole in the endometrial preparation for frozen thawed embryo transfer cycles and to compare it to the HRT with estrogen and progesterone.
The Study Design : Retrospective study.
Patients and Methods: 320 cycles of endometrial preparation for frozen thawed embryo transfer were analyzed from 1st of January 2015 to 31st of June 2017, the recruited patients were divided into two groups: Group1 (n =160): Induction of ovulation group (letrozole group ) and Group 2 (n = 160): Hormonal replacement therapy group (HRT group).
Results: the biochemical pregnancy rate was not significantly higher in the letrozole group 90 (56.3%) than in the HRT group 78 (48.8%) ; while the implantation rate, the clinical pregnancy rate and ongoing pregnancy rate were significantly higher in the induction group 22 (27.766), 81 (50.6%), 71 (44.4%) compared to HRT group 16.72 (24.096), 62 (38.8%), 44 (27.5%), respectively. First trimester abortion rate was significantly higher in the HRT group 19 (11.9%) compared to induction group 10 (6.3%).
Conclusion: The use of letrozole in patients undergoing FET was associated with significantly higher implantation rate, clinical pregnancy rate, ongoing pregnancy rate and a lower 1st trimesteric abortion rate, than use of HRT in frozen thawed embryo transfer cycles