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.