The impact of the interaction between ovarian markers and the endometrium on the outcomes of assisted reproduction

Objective To investigate the interaction effects of anti-Müllerian hormone (AMH), antral follicle count (AFC), basal follicle-stimulating hormone (FSH), and endometrial thickness on the outcomes of assisted reproductive technology (ART). Methods This retrospective cohort study included 12,071 infertile patients with endometrial thickness of 7–14 mm who underwent fresh embryo transfer at a large reproductive medical center in Chengdu, China, between 2019 and 2022. Optimal thresholds for AMH, AFC, and basal FSH were determined using receiver operating characteristic (ROC) curve analysis, and patients were subsequently stratified into relatively normal and abnormal ovarian response groups based on these cut-offs. Cox proportional hazards models were employed to assess the association between endometrial thickness and pregnancy outcomes, including biochemical pregnancy, clinical pregnancy, and live birth. Stratified analyses and interaction tests were further conducted to evaluate the modifying effects of AMH, AFC, and basal FSH levels on this association. Sensitivity analyses were performed to verify the robustness of the findings. Results Multivariable-adjusted Cox regression indicated that among patients with AMH ≥2.59 ng/mL or AFC ≥11, each 1-mm increase in endometrial thickness was associated with modest outcome improvements: a 1.5% increase in biochemical pregnancy rate [hazard ratio (HR) 95% confidence interval (CI): 1.015 (1.002, 1.029)], a 0.8% increase in clinical pregnancy rate [HR 95% CI: 1.008 (1.001, 1.015)], and a 0.7% increase in live birth rate [HR 95% CI: 1.007 (1.001, 1.013)]. Baseline FSH levels showed no significant association with pregnancy outcomes. Statistically significant interactions were observed between endometrial thickness and both AMH and AFC ( P -interaction < 0.05). Sensitivity analyses supported the robustness of these associations. Conclusion Among patients with normal ovarian reserve, endometrial thickness within the range of 7–14 mm showed a positive albeit modest association with ART pregnancy outcomes, with AMH and AFC levels exerting a modifying effect on this association.