Antihypertensive Treatment Adherence during Pregnancy by Race and Ethnicity.

Abstract

BACKGROUND Recent evidence from the Chronic Hypertension and Pregnancy (CHAP) trial demonstrates that treatment of even mild chronic hypertension during pregnancy reduces the risk of severe adverse maternal, fetal, and neonatal outcomes. Black patients are disproportionately affected by hypertension-related morbidity during pregnancy. Outside of pregnancy, substantial racial and ethnic differences in antihypertensive medication adherence have been reported. Insight into antihypertensive treatment adherence patterns during pregnancy may highlight approaches to decrease racial disparities in hypertension-related adverse pregnancy outcomes. OBJECTIVE To evaluate differences in antihypertensive treatment adherence during pregnancy by race and ethnicity. STUDY DESIGN Cohort study of a nationwide sample of publicly insured pregnant individuals nested in the Medicaid Analytic eXtract/Transformed Medicaid Statistical Information System Analytic Files, 2000-2018. Participants were pregnant individuals who initiated recommended antihypertensives (i.e., methyldopa, labetalol, or nifedipine) in the first half of pregnancy, with initiation defined as no antihypertensive medication dispensing during the 3 months before pregnancy. Differences in treatment adherence during pregnancy - defined as >80% of days covered in the second half of pregnancy - by race/ethnicity were evaluated. Potential confounders considered included socio-demographic characteristics, comorbidities and concomitant medication use. Risk ratios and their 95% CI were estimated using log-binomial regression; risk differences were estimated using binomial regression. Sensitivity analyses were conducted to assess the robustness of the findings. RESULTS The 16,554 hypertensive treatment initiators had a mean age of 29.4 years (standard deviation: 5.9); 7,376 (44.6%) were Black, 2,827 (17.1%) were Hispanic or Latino, 5,194 (31.4%) were White, and 1,157 (7.0%) had other/unknown race and ethnicity. The proportion of initiators with treatment adherence during the second half of pregnancy was considerably lower for individuals classified as Black (16.8%) compared to other race and ethnicity groups (range: 27.2-28.2%). After adjustment for patient characteristics, adherence to treatment was lower among Black individuals as compared to White individuals (risk ratio = 0.59 [95% CI: 0.54, 0.63]; risk difference = -9.91 [-11.71, -8.10] per 100 individuals). Treatment adherence was also lower for individuals categorized as Hispanic or Latino and other/unknown race and ethnicity compared to White individuals, but differences were less pronounced. Findings were consistent across sensitivity analyses, which included restricting the cohort to those with a recorded diagnosis of hypertension, restricting to term births, re-defining adherence as >80% days covered for any antihypertensive medication (i.e., allowing switches to antihypertensives other than methyldopa, labetalol, or nifedipine), and redefining adherence based on >50% days covered with recommended antihypertensives. CONCLUSIONS These findings suggest that adherence to antihypertensive treatment throughout pregnancy differs significantly by race and ethnicity among individuals who initiate treatment early in pregnancy. The considerably lower adherence among Black individuals is particularly concerning given that Black individuals with hypertension are at higher risk for adverse pregnancy outcomes. Defining strategies to improve adherence to antihypertensive treatment is important to reduce racial disparities in maternal morbidity.