Sequential blastocyst transfer improved pregnancy outcomes in patients undergoing frozen-thawed embryo transfer cycles: who will be the ultimate beneficiary.

BACKGROUND

Sequential embryo transfer (ET) is a recommended strategy for women with recurrent implantation failure (RIF), but it remains unclear which population may benefit from this strategy. The purpose of this study was to assess the value of sequential blastocyst transfer on pregnancy outcomes in frozen-thawed embryo transfer (FET) cycles and the indications for sequential blastocyst transfer.

METHODS

A total of 639 FET cycles were included in this retrospective study, of which 319 were in the conventional group and 320 were in the sequential group. After propensity score matching (PSM), there were 272 FET cycles in each group. Further stratified analyses were conducted based on age, number of previous failed cycles, and number of high-quality blastocysts. Pregnancy outcomes, such as clinical pregnancy rate (CPR), implantation rate, live birth rate (LBR), biochemical pregnancy loss rate, early miscarriage rate, ectopic pregnancy rate, multiple pregnancy rate, and rates of preterm birth and low birthweight in both singleton and multiple pregnancies, were compared between the two groups.

RESULTS

Compared to the conventional group, the sequential group had a higher CPR (65.4% vs. 54.4%, p = 0.009) and a lower multiple pregnancy rate (30.9% vs. 45.9%, p = 0.005). Stratified analyses revealed that, compared with the conventional group, the sequential group achieved a higher CPR (57.7% vs. 31.7%, p = 0.036) and implantation rate (36.5% vs. 20.7%, p = 0.044) among patients aged ≥ 40 years (exploratory analysis) and a lower multiple pregnancy rate (31.9% vs. 51.0%, p = 0.004) in patients aged < 35 years. Sequential blastocyst transfer was associated with a lower multiple pregnancy rate (27.8% vs. 48.8%, p = 0.036) and a higher LBR (58.4% vs. 41.7%, p = 0.041) in patients with 3 previous failed cycles, and a higher CPR (63.3% vs. 40.9%, p = 0.031) in patients with > 3 previous failed cycles. Additionally, for patients with 0 high-quality blastocysts, the sequential group yielded a higher CPR (54.5% vs. 39.8%, p = 0.032) and implantation rate (34.7% vs. 25.2%, p = 0.033) than the conventional group. All subgroup analyses are exploratory due to limited statistical power and multiple comparisons.

CONCLUSIONS

Patients with ≥ 3 previous failed cycles or 0 high-quality blastocysts, or patients aged ≥ 40 years, may benefit from the sequential blastocyst transfer strategy.