Optimising Luteinising Hormone Levels on Trigger Day for Improved Ovarian Response and Pregnancy Outcomes in Gonadotropin-Releasing Hormone Antagonist Protocols: A Retrospective Cohort Study

Objective: To determine the optimal luteinising hormone (LH) level on the trigger day and its impact on pregnancy outcomes in gonadotropin-releasing hormone (GnRH) antagonist protocols using a data-driven approach.

Design: Retrospective cohort study.

Setting: Third Affiliated Hospital of Guangzhou Medical University.

Population: Overall, 6107 in vitro fertilisation/intra-cytoplasmic sperm injection fresh embryo transfer cycles with GnRH-antagonist protocols were performed between January 1, 2018 and February 1, 2023.

Methods: Restricted cubic spline analysis and segmented regression identified the optimal LH threshold. Patients were categorised into low (≤ 1.6 IU/L) and high (> 1.6 IU/L) LH groups. Propensity score matching (PSM) and multivariable logistic regression were applied to adjust for confounding factors.

Main outcome measures: Live birth rate per embryo transfer cycle.

Results: The high LH group showed significantly higher live birth rates (42.9% vs. 36.9%, adjusted odds ratio [aOR]: 1.468; 95% CI: 1.220-1.766, p < 0.001), ongoing pregnancy rates (51.4% vs. 43.6%, aOR: 1.498; 95% CI: 1.338-1.678, p < 0.001), clinical pregnancy rates (52.4% vs. 45.6%, aOR: 1.439; 95% CI: 1.285-1.611, p < 0.001) and biochemical pregnancy rates compared with the low LH group, despite retrieving fewer oocytes (median 10 vs. 12, p < 0.001). These results remained consistent after PSM and multivariable logistic regression analysis.

Conclusions: Higher LH levels on the trigger day are associated with improved pregnancy outcomes in GnRH-antagonist protocols. Maintaining an optimal LH range is crucial for balancing oocyte yield and assisted reproductive technology success, highlighting the importance of individualised ovarian stimulation protocols.