The novel incorporation of aromatase inhibitor in hormonal replacement therapy cycles: a randomized controlled trial

Abstract

Research questionDoes the incorporation of the aromatase inhibitor, letrozole, in hormone replacement therapy (HRT) improve the pregnancy outcome in vitrified–warmed blastocyst transfer cycles? DesignA randomized controlled trial; HRT was used in all cycles. Exogenous oestradiol, 6 mg daily started on day 2 or day 3 of the cycle. Tri-laminar endometrium 9 mm or thicker was the targeted cut-off. Thereafter, participants were randomized into two groups. Group A (HRT plus letrozole): 2.5 mg oral letrozole was given twice daily for 5 days only with continuation of daily oestradiol. Then, daily intramuscular progesterone was started with continuation of oestradiol. Group B (HRT only): daily intramuscular progesterone was administered in addition to daily oestradiol. In both groups, good-quality day-5 blastocyst transfer was planned on the sixth progesterone day with continuation of oestradiol and progesterone. Ongoing pregnancy rate was the primary outcome. ResultsA total of 112 patients were randomized, 56 in each group. Three participants did not have good-quality blastocyst after warming (one in group A and two in group B) and were excluded from the study. Group A and B included 55 and 54 participants, respectively. Ongoing pregnancy rate was significantly higher in group A than group B (RR 1.39, 95% CI 1.04 to 1.86, P = 0.023). Additionally, clinical pregnancy rate was significantly higher in group A (RR 1.31, 95% CI 1.02 to 1.68, P = 0.030). ConclusionsA new protocol of incorporating letrozole in HRT cycles seems to significantly increase probability of pregnancy, compared with HRT alone.