1C-04 - The Comparative Effectiveness and Safety of Labetalol Versus Nifedipine for the Treatment of Chronic Hypertension During Pregnancy

Background: Clinical guidelines recommend treatment of mild and moderate chronic hypertension during pregnancy, with labetalol and nifedipine recommended as first-line medications.

Objectives: To compare the effectiveness and safety or labetalol and nifedipine for treatment of chronic hypertension in pregnancy.

Methods: We used a target trial emulation approach to compare new-users of labetalol and nifedipine. We obtained data for individuals with live- and stillbirths from the U.S. MerativeTM Marketscan® Research Database of commercial insurance claims for 2007 to 2022. We included individuals with chronic hypertension who were not taking antihypertensive medication treatment prior to pregnancy and then initiated treatment with labetalol or nifedipine within the first 20 weeks of pregnancy. The primary effectiveness outcome was the composite of preeclampsia with severe features, eclampsia, medically indicated preterm birth, placental abruption, or stillbirth. The primary safety outcome was an infant born small-for-gestational age. We used generalized linear models with a binomial distribution to estimate risk ratios (RR) and risk differences (RD) with 95% confidence intervals (CI), adjusting for confounding with stabilized inverse probability of treatment weights and high-dimensional propensity scores. We also compared treatments on each component of the composite outcome, and performed a sensitivity analysis restricted to individuals with preexisting diabetes or high comorbidity scores.

Results: We studied 6,724 pregnant individuals with chronic hypertension who initiated either labetalol (5,504, 82%) or nifedipine (1,220, 18%) in the first 20 weeks of pregnancy. The primary effectiveness outcome occurred in 42% in the labetalol group and 44% in the nifedipine group, with the fully adjusted RR of 0.99 (95% CI: 0.90, 1.08) and the fully adjusted RD of -0.55 per 100 births (95% CI:-3.61, 2.50). The primary safety outcome of small-for-gestational age was 13% in the labetalol group and 12% in the nifedipine group, with a fully adjusted RR of 0.95 (95% CI: 0.79, 1.14) and a fully adjusted RD of -0.63 per 100 births (95% CI:-2.67, 1.40). The results were consistent for each component of the composite outcome, and in subgroups with preexisting diabetes or high comorbidity scores.

Conclusions: This study suggests that labetalol and nifedipine have comparable effectiveness and safety when used for treatment of chronic hypertension during pregnancy.