Response variables
For repeated measures analysis, the primary response variable of interest was the SI value. The SI is a continuous variable that ranges from 0.7 to 0.9, with 0.7 meaning the minimum expected range and 0.9 meaning the maximum normal limit.13–16.SI was assessed immediately upon admission to the labour room in the active stage of labour (time 0), at the second stage of labour (time 1), and every 30 minutes until two hours postpartum (30-60-90-120 minutes, time 2 to 5).