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

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.

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.

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

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.

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.