Primary and secondary adherence to antihypertensive medications during pregnancy and postpartum

• Adherence to antihypertensive medications during pregnancy and postpartum has not been comprehensively studied. • In this electronic health records study, 72.6% patients had primary adherence during pregnancy and 73.4% during postpartum. • Secondary adherence during pregnancy was 63.6% among those with pre-existing hypertension. • Patient and healthcare provider race, blood pressure, obesity, insurance type, and parity were associated with adherence. To examine adherence to antihypertensive medications during pregnancy and postpartum among patients with hypertensive disorders of pregnancy (HDP).. Using electronic health records and healthcare claims data, we examined prenatal care patients aged 16–49 years from a health care system in Minnesota who delivered between 2009–2021, had continuous medical and pharmacy insurance coverage throughout pregnancy and up to 6 weeks postpartum, and had HDP (pre-existing/gestational hypertension, preeclampsia, HELLP syndrome, and eclampsia). Primary outcome was primary adherence to antihypertensives during pregnancy and up to 6 weeks postpartum, separately, defined as filling of first outpatient prescription within 7 days. Secondary outcome was secondary adherence during pregnancy among patients with pre-existing hypertension, defined as proportion of days covered, calculated using prescription fill data. We estimated risk ratios (RR) and 95 % confidence intervals (CIs) to assess associations between patient characteristics and adherence. Among 4,647 eligible patients, 526 (11.3%) and 987 (21.2%) had an outpatient antihypertensive prescription during pregnancy and postpartum, respectively. Primary adherence was observed for 72.6% patients during pregnancy and 73.4% during postpartum. Patients with Black versus White healthcare provider at their first prenatal visit were more likely to have primary adherence during pregnancy (RR 1.22, 95% CI 1.03–1.46) while severe blood pressure was associated with adherence during postpartum (RR 1.26, 95% CI 1.14–1.40). Secondary adherence during pregnancy was 63.6%. Patient race, obesity, health insurance type, and parity were associated with secondary adherence. Approximately 70% of eligible patients had primary adherence but secondary adherence was lower for antihypertensive treatment during pregnancy.