Multivariable risk model for postpartum re-presentation with hypertension: development phase

Abstract

Objectives: Postpartum hypertension is one of the leading causes of re-presentation to hospital postpartum and is associated with adverse long-term cardiovascular risk. Postpartum blood pressure monitoring and management interventions have been shown to reduce hospital re-presentation, complications and long-term blood pressure control. Identifying patients at risk can be difficult as 40%-50% present with de novo postpartum hypertension. We aim to develop a risk model for postpartum re-presentation with hypertension using data readily available at the point of discharge.

Design: A case-control study comparing all patients who re-presented to hospital with hypertension within 28 days post partum to a random sample of all deliveries who did not re-present with hypertension. Multivariable analysis identified risk factors and bootstrapping selected variables for inclusion in the model. The area under the receiver operator characteristic curve or C-statistic was used to test the model's discriminative ability.

Setting: A retrospective review of all deliveries at a tertiary metropolitan hospital in Melbourne, Australia from 1 January 2016 to 30 December 2020.

Results: There were 17 746 deliveries, 72 hypertension re-presentations of which 51.4% presented with de novo postpartum hypertension. 15 variables were considered for the multivariable model. We estimated a maximum of seven factors could be included to avoid overfitting. Bootstrapping selected six factors including pre-eclampsia, gestational hypertension, peak systolic blood pressure in the delivery admission, aspirin prescription and elective caesarean delivery with a C-statistic of 0.90 in a training cohort.

Conclusion: The development phase of this risk model builds on the three previously published models and uses factors readily available at the point of delivery admission discharge. Once tested in a validation cohort, this model could be used to identify at risk women for interventions to help prevent hypertension re-presentation and the short-term and long-term complications of postpartum hypertension.

Keywords: clinical decision-making; hospital medicine; machine learning; obstetrics and gynecology; risk management.

Figure 1

Flow chart for selection of randomised sample controls (left) and hypertension re-presentation cases (right). ICD, International Classification of Disease; HITH, hospital in the home; HTN, hypertension.

Figure 2

ROC curve. Variables included gestational hypertension, pre-eclampsia, grouped median peak systolic blood pressure in the delivery admission >=3 hypertensive blood pressure readings in the delivery admission, elective caesarean delivery and aspirin prescription. ROC, receiver operating characteristic.