Strategy-Based Comparison of Fresh Double Embryo Transfer Versus Sequential Single Embryo Transfers in Women With Adequate Blastocyst Availability.

Objective

To compare the cumulative reproductive outcomes of two embryo transfer strategies in women with adequate blastocyst availability: immediate fresh double embryo transfer (DET) and a sequential strategy consisting of fresh single embryo transfer (SET) followed by frozen-thawed SET derived from the same retrieval cohort.

Design

A retrospective cohort study was conducted at Taipei MacKay Memorial Hospital using clinical data from January 2017 to December 2023.

Setting

A single tertiary reproductive center.

Subjects

Women younger than 40 years with normal ovarian reserve and ≥ two good-quality blastocysts obtained from a single stimulation cycle.

Exposure

Patients underwent either fresh DET or sequential SET that included a second transfer within three years.

Main outcome measures

Cumulative clinical pregnancy rate (CCPR) and cumulative live birth rate (CLBR) per retrieval cycle.

Results

A total of 256 patients were included: 135 in the sequential SET group (33.39 ± 3.13 years) and 121 in the fresh DET group (35.41 ± 2.87 years). The CCPR was significantly higher in the sequential SET group than in the fresh DET group (86.7% vs.61.2%; RR: 1.42, 95% CI: 1.21-1.66), as was the CLBR (63.7% vs.51.2%; RR: 1.24, 95% CI: 1.00-1.54). Although the initial pregnancy rate was lower in the group who would have sequential SET than fresh DET (41.4% vs.61.2%), cumulative pregnancy outcomes improved substantially after the second transfer in the SET cohort. The miscarriage rate did not differ significantly between the sequential SET and fresh DET groups (24.7% vs. 14.9%; RR: 1.67, 95% CI: 0.89-3.13), whereas the twin pregnancy rate was markedly lower (0% vs.14.9%, p < 0.001) in the sequential SET group. Based on pooled neonatal data irrespective of plurality, mean gestational age (38.47 vs.37.41 weeks, p = 0.69) and mean birth weight (3065 vs.2773 g, p = 0.09) were comparable between groups. Preterm births per oocyte retrieval cycle were significantly less frequent following sequential SET than fresh DET (2 vs.16, p < 0.001).

Conclusions

Among patients with favorable embryo availability, sequential SET demonstrated higher cumulative reproductive outcomes within a strategy-based framework than fresh DET. These findings reflect differences in embryo utilization pathways rather than in isolated transfer efficacy; they should be interpreted in the context of treatment continuation and cohort selection.