Supplementary Material for: Effect of gonadotropin dose reduction during COH on progesterone levels and embryo outcomes in women undergoing IVF/ICSI-ET with GnRH-A protocol

Objectives: This study investigates the impact of reduced gonadotropin doses during controlled ovarian hyperstimulation (COH) on progesterone levels in the late follicular phase of IVF/ICSI-ET. Design: A retrospective cohort study employing propensity score matching (PSM) to balance groups. Participants/Materials: Infertile patients undergoing IVF/ICSI-ET at the Reproductive Medicine Center of the 900th Hospital from January 2017 to July 2020. Setting: Reproductive Medicine Center, 900th Hospital of the Joint Logistics Team, formerly Fuzhou General Hospital. Methods: A total of 1380 patients were enrolled; 670 received reduced gonadotropin doses (12.5-75 units/day from days 6-8) and 710 underwent routine treatment. The primary outcome measured was progesterone levels on trigger day. Results: Progesterone levels on trigger day were significantly lower in the gonadotropin dose reduction group (1.24±0.51) compared to the control group (1.34±0.53, P<0.001). The proportion of patients with P ≥ 1.5 ng/ml was significantly lower in the gonadotropin dose reduction group compared to the control group (22.7% vs. 29.9%, P=0.003).Multivariable logistic regression indicated that dose reduction decreased the risk of progesterone elevation [OR=0.535, 95% CI: 0.404-0.709]. Limitations: The study is limited by its retrospective design, which may introduce biases. Conclusions: Reducing gonadotropin doses during COH may lower elevated progesterone levels in the late follicular phase, potentially improving embryo outcomes in IVF/ICSI-ET.