One plus one is better than two. The best choice for embryo transfer: A retrospective cohort study

Objective: To assess the freeze-only strategy associated with frozen-thawed single-embryo transfers (SETs) efficiency in high-responder patients. Design: Retrospective cohort study Setting: Private reproductive medicine center. Population: A total of 500 IVF cycles with freeze-all embryos followed by elective frozen-thawed embryo transfers (eFET). Method: Elective double-embryo transfer (eDET) group with 291 cycles, in which two embryos were placed in the first eFET, and elective-SET (eSET) group with 209 cycles, in which the patients underwent eSET in their first eFET. For those who did not become pregnant, a second SET was performed (n=60). Main outcome measures: The ongoing pregnancy rate (PR) was compared after the first FET, and cumulative ongoing PR was evaluated for the SET group considering patients who had a second frozen-thawed SET (eSET + SET). Results: No significant differences were observed in the ongoing PR after the first FET (eDET: 37.8% versus eSET: 34.8%, p = 0.497). The estimated cumulative ongoing PR for eSET + SET (52.1%) was significantly higher than eDET (37.8%, p < 0.001). The linear multiple regression confirmed that transfer of two embryos in sequential SETs led to a higher chance of implantation than did the transfer of two embryos together (eDET; coefficient: 0.142, p < 0.001). The eDET group had 26.9% twin pregnancies compared with 1.9% in the eSET (p < 0.001). Conclusions: Sequential SETs in freeze-only cycles may be the best option to attain high success rates in high-responder patients, leading to an increased chance of implantation and avoidance of multiple gestations.