Is duration of estrogen supplementation associated with clinical outcomes in frozen-thawed autologous single-blastocyst transfer cycles?

PURPOSE: To investigate the relationship between different duration of estrogen administration and live birth rate (LBR) after autologous single frozen blastocyst transfer with hormone replacement therapy. METHODS: A total of 2026 frozen blastocyst transfer cycles in the assisted reproductive center of northwest women and children’s hospital from January, 2017, to August, 2020, were retrospectively analyzed. All the cycles were allocated into 3 groups according to the duration of estrogen administration: group A, 11–14 days (n = 346); group B, 15–18 days (n = 1191), and group C, ≥ 19 days (n = 489). Baseline data, clinical, and perinatal outcomes of the three groups were compared. A multivariate regression model was constructed to analyze the association between duration of estradiol administration and clinical outcomes. RESULTS: We did not observe a significant association between duration of estrogen supplementation and LBR in group B (adjusted odds ratio [aOR] 1.14; 95% confidence interval [CI], 0.89–1.45) or group C (aOR 1.16; 95% CI, 0.86–1.56) patients with group A as the reference group, through logistic regression analysis. No statistical differences were observed in perinatal outcomes among the three groups. CONCLUSION: The duration of estrogen administration was not associated with the likelihood of live birth in women undergoing frozen-thawed autologous single-blastocyst transfer. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10815-022-02481-5.