Received July 11, 2021
Accepted November 29, 2021

Objective:To determine whether elective frozen embryo transfer (eFET) is associated with better cumulative clinical outcomes compared with fresh embryo transfer (ET) in in vitro fertilization (IVF) cycles. Methods:A comparison of cumulative outcomes between the eFET and the fresh ET groups were performed. The analysis was performed in four groups of patients based on the number of retrieved oocytes: Group 1 – poor-responders (1–3 oocytes); Group 2 – suboptimal-responders (4–9 oocytes); Group 3 – normal-responders (10–15 oocytes); and Group 4 – hyper-responders (>15 oocytes). The primary outcome was the cumulative live birth rate (CLBR) per cycle. Results:A total of 7,236 IVF/intracytoplasmic sperm injection(ICSI) cycles and 10,283 ETs (n=5,639 in the eFET group; n=4,644 in the fresh group). The freeze-all strategy is associated with improved CLBRs in normal and hyper-responders, but not in suboptimal and poor responders. In Group 1, the CLBR was 14.3% and 17.7% (P=0.584) for the eFET and fresh group, respectively. In Group 2, the CLBR was 25.1% and 23.3% (P=0.083) in the eFET and fresh group, respectively. In Group 3, the CLBR was 40.5% in the eFET and 36.6% in the fresh group (P<0.001; aOR = 1.58; 95% CI: 1.26–1.98). In Group 4, the CLBR was 52.2% and 47.7% (P <0.001) in the eFET and fresh group, respectively (aOR = 1.67; 95% CI: 1.31–2.12). Conclusion:The implementation of the freeze-all strategy should be individualized, as it is associated with improved cumulative live birth rates (CLBRs) in normal and hyper-responders, but not in suboptimal and poor responders.