Letrozole versus artificial hormonal endometrial preparation for vitrified–warmed embryos transfer cycles

Objective: To evaluate the efficacy of letrozole in the endometrial preparation of vitrified–warmed embryo transfer cycles and to compare it to the hormonal preparation with estradiol valerate and progesterone study. Design: Retrospective observational study. Methods: We analyzed 197 cycles of endometrial preparation for vitrified–warmed embryo transfer from January 2013 to August 2014. A final 94 cycles of letrozole were compared to 96 cycles of hormonal preparation. Results: Pregnancy rate was non significantly higher in the letrozole group (53.2%) than in the hormonaly prepared group (40.6%) while the ongoing pregnancy rate was significantly higher in the letrozole group 47.9% v 32.3% (P value 0.02). The abortion rate was non significantly lower in the letrozole group 5.3% v 8.3%. The mean endometrial thickness in the hormonaly prepared group was significantly higher than the letrozole 9.9 mm ± 1.7 and 9.1 mm ± 1.6 respectively. Conclusion: Endometrial preparation for vitrified-warmed embryo transfer using the aromatase inhibitor letrozole has a significantly higher ongoing pregnancy rate than that of the hormonal preparation.