Data collection
Two qualified nurses obtained all data. Clinical characteristics
included maternal age, height, weight, body mass index (BMI), parity,
gestational age (GA), and haemoglobin concentration. The SI was defined
as the ratio of HR to SBP.23 to measure HR and SBP,
which was measured using a digital calibrated sphygmomanometer (Omron M6
Comfort, OMRON Healthcare, Kyoto, Japan). For all cases, at least seven
measures of the SI were obtained: 1) at the active phase of the first
stage of labour, 2) during the second stage of labour, 3) within 15 min
postpartum, and 3) every 30 minutes until two hours postpartum (four
measures). All SI values were masked by the treating clinicians and used
only for research purposes. Based on the World Health Organization
criteria, maternal anaemia was defined as less than or equal to 11
g/L.24 The presence of PPH as registered on the
clinical charts was also recorded. All patients were followed up until
their discharge.