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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