Association between NLA and SI values across repeated measurements
The crude trends and 95% CI of the multilevel regression model across repeated measures for SI, HR, and SBP are shown in Figure 1(a-c) . The mean raw values of SI, HR, and SBP are shown inFigures 1a, 1b, and 1c, respectively (as dots).
In our sample, the SI was higher in women with NLA, and this difference increased as labour progressed. This association can also be seen in the raw mean SI values (Table 2 ). At the start of the first stage of labour, the mean difference in SI between the NLA and non-NLA groups was 0.04, and this raw mean difference increased to 0.10 after 120 minutes of the postpartum period.
These differing trends in the SI continued after adjustments in the multilevel model (Table S2). Figure 2(a-c) shows the adjusted association between NLA and SI in labour and postpartum women, including β-coefficients and 95% CI. After adjusting the multilevel model by age, nulliparity, and dilation, the mean SI without NLA across the measurements was 0.69, while in the NLA group, it was 0.76 (for a mean difference of 0.067).