Risk of postpartum readmission after hypertensive disorder of pregnancy and variation by discharge antihypertensive medication prescription

Background Patients with hypertensive disorders of pregnancy have a high rate of postpartum readmission. Objectives We evaluated whether type of antihypertensive medication prescribed at discharge was associated with postpartum readmission after a hypertensive disorder of pregnancy. Study Design A retrospective cohort of 57,254 pregnancies with hypertensive disorders of pregnancy that began between 2012-2018 in the electronic obstetric database of Kaiser Permanente Northern California. Postpartum readmissions occurred within 6 weeks of discharge from the delivery hospitalization. Cox regression models evaluated associations between type of antihypertensive medication prescription at discharge (none, labetalol only, nifedipine only, two or more antihypertensive medications) with postpartum readmission, adjusted for type of hypertensive disorder of pregnancy, final inpatient systolic and diastolic blood pressures, age, body mass index, mode of delivery, insurance status, race/ethnicity, delivery facility, comorbidity score, smoking, preterm delivery, parity, and neighborhood deprivation index. Results Among eligible patients with a hypertensive disorder of pregnancy, 1696 (3.0%) were readmitted within 6 weeks. Approximately 86% of patients were discharged without antihypertensive medication; among those discharged with a prescription for antihypertensive medication, most were prescribed either labetalol only (54%) or nifedipine only (30%). Unadjusted readmission risk was highest among patients discharged with labetalol only (7.6%), lower for patients discharged with nifedipine only (3.6%) or two or more antihypertensive medications (3.2%), and lowest for those discharged without a prescription for antihypertensive medication (2.5%). In adjusted models, compared to discharge without antihypertensive medication, discharge on labetalol only was associated with 63% (hazard ratio: 1.63; 95% confidence interval: 1.41, 1.88) greater incidence of postpartum readmission, while discharge on nifedipine only or on two or more antihypertensive medications were associated with 26% and 47% lower incidence of postpartum readmission, respectively (hazard ratios: 0.74 (95% confidence interval: 0.59, 0.93); 0.53 (95% confidence interval: 0.38, 0.74), respectively). There was no strong evidence to suggest that the effect of discharge antihypertensive medication type on incidence of readmission varied by race and ethnicity (interaction p=0.88). Results indicating an elevated risk for labetalol were consistent in models excluding patients with pre-pregnancy hypertension. Conclusions Discharge on nifedipine alone or multiple antihypertensive medications (versus no medication) were associated with lower incidence of readmission, while discharge on labetalol alone was associated with elevated readmission incidence. Large-scale, prospective research to compare effectiveness of commonly prescribed hypertension medications at discharge is warranted.