Different endometrial preparation protocols on first frozen-thawed embryo transfer outcomes after hysteroscopic polypectomy: A retrospective cohort study

Objective: To evaluate the optimal endometrial preparation protocol for frozen-thawed embryo transfer (FET) following hysteroscopic polypectomy. Methods: This was a retrospective clinical cohort study involving 464 patients who underwent their first FET after polyp resection between January 2021 and July 2023. The cohorts were categorized into three groups: the natural cycle (NC) group (n = 139), the ovarian induction (OI) group (n = 117), and the hormone replacement therapy (HRT) group (n = 208). Results: In the initial unadjusted analysis, both NC and OI cycles exhibited similar pregnancy rates but were associated with significantly higher implantation rate (56.5%, 57.1% vs 42.0%, P < 0.001), clinical pregnancy rate (73.4%, 74.4% vs 57.2%, P = 0.001), and ongoing pregnancy rate (OPR; 67.6%, 63.2% vs 51.0%, P = 0.005) compared to the HRT group. Additionally, the three groups demonstrated comparable abortion rate (7.8%, 14.9% vs 10.9%, P = 0.299). After adjusting for potential confounders in the multiple logistic regression model, the HRT protocol resulted in a 54% significantly lower OPR compared to the NC protocol (adjusted odds ratio [aOR] = 0.46, 95% confidence interval [CI]: 0.28-0.77; P = 0.003). Meanwhile, the OPR difference between the OI protocol and the NC protocol remained insignificant (OI vs NC: aOR = 0.62, 95% CI: 0.35-1.12; P = 0.112). Conclusion: The ovulatory-FET scheme (NC and OI) following hysteroscopic polyp resection displayed promising clinical outcomes compared with HRT-FET scheme. The regimen without exogenous estrogen administration should be prioritized for endometrial preparation protocol after polypectomy.