Impacts of the COVID-19 pandemic on early pregnancy outcomes among women undergoing frozen-thawed embryo transfer: a retrospective cohort study.

The effect of COVID-19 pandemic on early pregnancy outcomes among women undergoing frozen-thawed embryo transfer (FET) remains unclear. We aimed to evaluate whether early pregnancy outcomes were altered in patients undergoing FET during the pandemic. In this retrospective cohort study, women conceived through FET in 2016-2021 from two hospitals in China were included. The early pregnancy outcomes were compared using Logistic regression model, including biochemical pregnancy rate (BPR), clinical pregnancy rate (CPR), and early pregnancy loss rate (EPLR). A total of 16,669 (67.2%) and 6,113 (26.8%) FET cycles enrolled before and during the pandemic, respectively. Univariate analyses showed that women undergoing FET during the pandemic had significantly increased BPR (72.9% vs. 69.7%) and CPR (59.5% vs. 55.0%), and significantly decreased EPLR (13.7% vs. 16.7%) compared to pre-pandemic (all P < 0.001). Moreover, after adjustment, the results were in accordance with univariate analysis for CPR [adjusted OR (95%CI) = 1.08 (1.01-1.14)] and EPLR [adjusted OR (95%CI) = 0.82 (0.73-0.91)], while the statistical significance between BPR and the pandemic disappeared. In summary, women conceived by FET did not have a reduced possibility of clinical pregnancy and a higher risk of early pregnancy loss during the pandemic compared with the pre-pandemic.