Obstetric early warning system to predict maternal morbidity of pre-eclampsia, postpartum hemorrhage and infection after birth in high-risk women: a prospective cohort study

OBJECTIVE: The purpose of early warning systems is to detect deterioration of the patient and to enable timely intervention to prevent possible severe illness. The most common causes of maternal morbidity and mortality after birth are worsening pre-eclampsia, postpartum haemorrhage and puerperal infection. Our aim was to validate the accuracy of the obstetric early warning system and different physiological triggers to predict morbidity on the postnatal ward in high-risk women. DESIGN: A prospective cohort study. SETTING: A tertiary referral hospital in Finland. PARTICIPANTS: High-risk women (n=828) (body mass index > 35 kg/m2, postpartum haemorrhage > 1,500 g, pre-eclampsia, chorioamnionitis during birth, type 1 diabetes or anxiety over the maternal condition based on clinical judgement) were studied on the postnatal ward in the first 24 hours after giving birth. In this study population the women without any morbidity served as a control group. The study was conducted between 1.11.2016 - 30.4. 2018 covering a period of 18 months. MEASUREMENTS AND FINDINGS: The accuracy of the obstetric early warning system and its five physiological parameters-respiratory rate, oxygen saturation, blood pressure, heart rate and body temperature-and a pain score to predict worsening pre-eclampsia, complications related to postpartum haemorrhage and puerperal infection were determined. A red trigger is as a single, markedly abnormal observation, and a yellow trigger is a combination of two mildly abnormal observations. The sensitivity of obstetric early warning system at its best was 72% for pre-eclampsia, 52% for infection and 25% for postpartum haemorrhage. The red triggers were significantly associated with morbidity in each outcome studied. The red triggers of systolic blood pressure (OR 25.7, 95% CI 13.2-50.1) and diastolic blood pressure (OR 22.1, 95% CI 11.3-43.0) were independently associated with pre-eclampsia, systolic blood pressure (OR 2.7, 95% CI 1.4-5.6) and heart rate (OR 3.6, 95% CI 1.7-7.6) with postpartum haemorrhage and heart rate (OR 3.3, 1.0-10.3) with infection. KEYCONCLUSIONS: The sensitivity of obstetric early warning system varied depending on the type of morbidity. The highest sensitivity and positive predictive value were in pre-eclampsia. Systolic and diastolic blood pressure and heart rate were the strongest physiological parameters to predict morbidity. IMPLICATIONS FOR PRACTICE: The systematic use of obstetric early warning system helps to improve maternal safety after birth in high-risk women. Blood pressure and pulse are the most important measurements.