Risk factors for postpartum readmission for preeclampsia or hypertension before delivery discharge among low-risk women: a case-control study

BACKGROUND: Postpartum hypertension or preeclampsia is one of the most frequent reasons for readmission after delivery discharge, and risk factors for readmission remain poorly characterized. OBJECTIVE: This study aimed to determine risk factors of postpartum readmission for hypertension or preeclampsia among low-risk women before delivery discharge. STUDY DESIGN: We conducted a nested case-control study from 2012 to 2015 at a tertiary care medical center. Cases were identified using diagnostic codes for postpartum transient hypertension, mild preeclampsia, severe preeclampsia, eclampsia, superimposed preeclampsia, and unspecified hypertension and readmission within 6 weeks of delivery. Controls not readmitted for hypertension or preeclampsia were time matched within 4 weeks of the delivery date to each case. We fit multivariable logistic regression models to identify independent risk factors for postpartum readmission for hypertension or preeclampsia and then calculated a receiver operating characteristic curve of the final model to assess model discrimination. RESULTS: Within the source cohort resulting in 58 cases and 232 matched controls, the rate of postpartum readmission for preeclampsia or hypertension was 0.4% (n=58 of 14,503). The median time to readmission was 6 days (range, 2-15 days), and 40% of cases had an outpatient postpartum visit before readmission. In multivariable analysis, non-Hispanic black race (adjusted odds ratio, 2.14; 95% confidence interval, 0.99-4.59), gestational hypertension (adjusted odds ratio, 2.70; 95% confidence interval, 1.12-6.54), preeclampsia during delivery admission (adjusted odds ratio, 3.12; 95% confidence interval, 1.29-7.50), and maximum postpartum systolic blood pressure during delivery admission (adjusted odds ratio, 1.05; 95% confidence interval, 1.03-1.08) were risk factors for readmission. This model had a good discriminative ability to predict women who would require readmission for preeclampsia or hypertension (area under the curve, 0.83; 95% confidence interval, 0.74-0.89). Using these 4 factors to illustrate this model, the predicted risk of readmission ranged from <1% in the lowest risk scenario (eg, postpartum systolic blood pressure of 120 mm Hg + no hypertensive disorders of pregnancy + white race) to 26% in the highest risk scenario (eg, postpartum systolic blood pressure of 160 mm Hg + preeclampsia + black race). CONCLUSION: Risk factors of postpartum readmission for hypertension or preeclampsia can be identified at the time of delivery discharge among low-risk women, regardless of an antenatal hypertensive disorder. A next step could be using these risk factors to develop a predictive model to guide postpartum care.