(1184) Tighter blood pressure control targets to reduce adverse pregnancy outcomes for patients with chronic hypertension

Objective: The Chronic Hypertension and Pregnancy (CHAP) Trial demonstrated improved outcomes for pregnant women with mild chronic hypertension (HTN) assigned strict blood pressure (BP) target of ≤ 140/90 compared to controls with target of ≤ 160/110. CHAP-based treatment guidelines were implemented at our health system in 2022. We hypothesize that implementation of CHAP guidelines in a large, socio-demographically diverse population reduced HTN-related morbidity.

Study Design: This is a retrospective cohort study of singleton pregnancies with a known or new diagnosis of mild HTN receiving prenatal and delivery care at a large regional health system in 2021 and 2023. In April 2022, BP targets of ≤ 140/90 were implemented. We compared 2021 with 2023 deliveries, with 2022 a washout period. Multiple gestations, major fetal anomalies, > 1 baseline antihypertensive, phospholipid syndrome or HTN-related cardiac or kidney disease were excluded. Primary outcome per CHAP was a composite of medically indicated preterm birth before 35 weeks, superimposed preeclampsia with severe features, placental abruption & perinatal death. Secondary outcomes included small-for-gestational-age and preterm birth before 37. Outcome adjusted odds ratios were generated via regression analyses controlling for maternal age, body mass index, public insurance, history of preeclampsia, and pre-existing diabetes.

Results: Of 1626 pregnant women with HTN, 134 were excluded for twins, congenital anomalies, >1 baseline antihypertensive or HTN-related comorbidities. Of the 1492 remaining, 710 were pre-, while 782 were post-implementation. The post-intervention group had higher BMI and higher public payor insurance status (Table 1). The primary composite outcome occurred in 30.9% of pre-implementation pregnancies compared to 29.2% of post-implementation pregnancies (aOR 0.84, 95% CI 0.66-1.09). Medically indicated delivery before 35 weeks was lower in the post-intervention group (10.4% vs 12.1%, aOR 0.7, 95% CI 0.47-0.99, Table 2).

Conclusion: Tighter BP control targets did not reduce the CHAP-defined outcome.