Accumulation of embryos to improve outcomes in advanced-age women undergoing IVF/ICSI cycles: a retrospective cohort study.

OBJECTIVE

To investigate the effect of the embryo accumulation strategy prior to embryo transfer on reproductive outcomes among advanced-age women undergoing IVF/ICSI treatment.

METHODS

This retrospective study included 970 advanced-age female patients undergoing in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) treatment at the Second Hospital of Hebei Medical University from 2012 to 2022. Participants were stratified into two groups according to the implementation of the embryo accumulation strategy before embryo transfer. The embryo accumulation group comprised 325 patients who completed ≥2 consecutive oocyte retrieval cycles and yielded at least one transferable embryo. The control group included 645 patients who underwent a single oocyte retrieval cycle and received embryo transfer with available transferable embryos. To eliminate baseline confounding bias, 1:1 propensity score matching (PSM) was applied. Ultimately, 299 matched pairs (598 patients) were successfully matched. Baseline clinical characteristics, laboratory indicators, and pregnancy outcomes were compared between the two cohorts before and after PSM. Multivariable logistic regression models were constructed to assess the independent effect of embryo accumulation on pregnancy outcomes. Restricted cubic spline and threshold effect analyses were performed to explore the nonlinear association between cumulative embryo number and reproductive outcomes. The primary study endpoint was cumulative live birth rate (CLBR), and the secondary endpoint was cumulative clinical pregnancy rate (CCPR).

RESULTS

After PSM, the biochemical pregnancy rate, CLBR and CCPR in the embryo accumulation group were all significantly higher than those in the control group (P < 0.001). However, no statistically significant difference was observed in the miscarriage rate between the two groups (P = 0.583). Binary logistic regression analysis based on the fully adjusted model (Adjust II) demonstrated that embryo accumulation was correlated with increased CLBR (OR = 2.75, 95% CI: 1.87-4.05, P < 0.001) and CCPR (OR = 2.71, 95% CI: 1.87-3.92, P < 0.001). Smooth curve fitting and threshold effect analysis were performed within the embryo accumulation group. CLBR and CCPR increased with the rise in cumulative embryo number when the cumulative embryo number was ≤ 2 (OR = 3.11, 95% CI: 1.27-8.50, P = 0.0181; OR = 3.59, 95% CI: 1.47-9.74, P = 0.0073). When the cumulative embryo number was > 2, CLBR and CCPR still presented a mild upward trend, but such trends did not reach statistical significance (OR = 1.06, 95% CI: 0.91-1.23, P = 0.4216; OR = 1.11, 95% CI: 0.97-1.29, P = 0.1326).

CONCLUSIONS

Among advanced-age women receiving IVF/ICSI treatment, embryo accumulation via consecutive stimulation cycles can significantly improve CLBR and CCPR, and the clinical benefits are prominent when the number of accumulated embryos does not exceed two. This strategy effectively optimizes reproductive outcomes for advanced patients undergoing assisted reproductive technology (ART). Nevertheless, due to the limitations of this retrospective study and unadjusted confounding factors, embryo quantity should not be the sole basis for clinical decisions. Individualized treatment strategies shall be developed based on a comprehensive assessment of patients' age, physical status and economic conditions.