Postpartum blood pressure control and the rate of readmission

Postpartum hypertension is a major contributor to the rising maternal mortality rates in the United States, with nearly half of maternal deaths occurring after delivery. Previous studies have found evidence that the maximum blood pressure reading during labor and delivery admission can predict readmission; however, the optimal blood pressure to reduce the need for readmissions and additional medical treatment in the postpartum period is not known.

This study aimed to investigate the relationship between postpartum blood pressure control at discharge and readmission within the first 6 weeks after delivery.

Data were obtained from Cosmos, an electronic health record-based, Health Insurance Portability and Accountability Act-defined limited dataset that includes more than 1.4 million birth encounters. All birthing parents with blood pressure data after delivery were included. Demographic information, medications, and readmissions were queried from the dataset. Patients were grouped into categories based on blood pressure readings in the 24 hours before discharge (≥160/110, ≥150/100, ≥140/90, ≥130/80, ≥120/80, and <120/80 mm Hg). The readmission rates across these groups were compared. Planned subanalyses included stratification by the use of antihypertensive medications and a sensitivity analysis using the highest blood pressure during admission. Covariates included maternal age, preexisting diabetes mellitus or lupus erythematosus, and body mass index.

The analysis included 1,265,766 total birth encounters, 391,781 (30.9%) in the referent group (120/80 mm Hg), 392,592 (31.0%) in the group with <120/80 mm Hg, 249,414 (19.7%) in the group with ≥130/80 mm Hg, 16,125 (1.3%) in the group with ≥140/90 mm Hg, 50,659 (4.0%) in the group with ≥150/100 mm Hg, and 20,196 (1.6%) in the group with ≥160/110 mm Hg. In the first 6 weeks after delivery, readmission rates increased with higher blood pressure readings. More than 5% of postpartum patients with the highest blood pressure readings (≥160/110 mm Hg) were readmitted. These patients were almost 3 times more likely to be readmitted than patients whose highest blood pressure reading fell into the referent group (120/80 mm Hg) (odds ratio [OR], 2.90; 95% confidence interval, 2.69-3.12). Patients with blood pressures of >150/100 mm Hg (odds ratio, 2.72; 95% confidence interval, 2.58-2.87), >140/90 mm Hg (odds ratio, 2.03; 95% confidence interval, 1.95-2.11), and >130/80 mm Hg (odds ratio, 1.43; 95% confidence interval, 1.37-1.49) all had higher odds of readmission, whereas patients with a blood pressure of <120/80 mm Hg had a lower odds of readmission (odds ratio, 0.78; 95% confidence interval, 0.75-0.81). Patients who had higher blood pressures during admission but had improved control in the 24 hours before discharge had lower rates of readmission than those whose blood pressures remained elevated. In all blood pressure categories, patients who received an antihypertensive prescription had higher rates of readmission.

In this large, national dataset, blood pressure control at discharge and readmission in the postpartum period were significantly correlated. Our data should inform postpartum hypertension treatment goals and the role of remote monitoring programs in improving maternal safety.