Statistical analysis
We used a fixed sample size from the primary trial, and all randomized participants were included in this analysis. Data analysis was performed using the modified intention-to-treat principle. All randomized women were included in the high-risk category II FHR tracing analysis; 96.4% (135/140) participants with validated paired Uv and Ua gases were included in the Ua lactate analysis; and 85% (119/140) participants were included in the Ua metabolites analysis. The Kolmogorov–Smirnov test was used to analyze the distribution of continuous variables. Baseline characteristics and outcomes were compared between the two groups using the Student’s 