Optimizing embryo transfer strategies for women with previous cesarean delivery: A propensity score-matched comparison of fresh versus frozen-thawed cycles.

OBJECTIVE

The optimal embryo transfer strategy for women with a history of cesarean delivery (CD) remains highly controversial. CD causes uterine microenvironmental damage, especially cesarean scar niche formation and chronic low-grade inflammation, both of which severely impair endometrial receptivity. Supraphysiological hormones during controlled ovarian stimulation (COS) further exacerbate these harmful conditions, creating a "double hit" that compromises implantation. This study aimed to compare the reproductive outcomes of fresh embryo transfer (fresh ET) versus a "freeze-all" frozen-thawed embryo transfer (FET) strategy in this specific population.

METHODS

A large-scale retrospective cohort study was conducted including women with a history of a single CD undergoing their first or second in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) cycle. To minimize selection bias and balance baseline and embryological covariates, a 1:1 propensity score matching (PSM) was performed. The primary outcome was the live birth rate (LBR) per transfer.

RESULTS

Following PSM, 412 well-matched pairs (n = 824 cycles) were analyzed. The FET group was found associated with a significantly higher LBR compared to the fresh ET group (42.2% vs 33.5%; odds ratio [OR] 1.45, 95% confidence interval [CI]: 1.12-1.88, P = 0.006) per transfer. Similarly, the clinical pregnancy rate (CPR, 51.5% vs 41.0%, P = 0.003) and implantation rate (35.8% vs 28.6%, P < 0.001) were found associated with the FET cohort, with no significant differences in miscarriage or adverse neonatal outcomes. Multivariate logistic regression found FET to be independently associated with live birth as a protective predictor (adjusted OR 1.48, 95% CI: 1.15-1.92, P = 0.003). Crucially, subgroup analysis found that the superiority of FET was predominantly associated with patients with a sonographically confirmed cesarean scar niche (OR 2.15, 95% CI: 1.45-3.20, P < 0.001), whereas the benefit was marginal in those with an intact scar (P = 0.125).

CONCLUSION

For women with a previous CD, a "freeze-all" strategy significantly improves LBR and implantation potential compared to fresh ET. This approach is strongly recommended, particularly for patients with a cesarean scar niche, who are the key population benefiting most from FET cesarean.