A NEW study has shown that the highest rates of severe maternal morbidity (SMM) at delivery are observed in patients with preeclampsia, both with and without chronic hypertension, while uncomplicated chronic hypertension without preeclampsia carry nearly the same risk as normotensive pregnancies.
Hypertensive disorders of pregnancy, including chronic hypertension, preeclampsia, and gestational hypertension, are major contributors to maternal morbidity and mortality. However, prior studies have often included patients with preexisting organ disease, making it unclear whether chronic hypertension alone, without preeclampsia, significantly increases the risk of SMM. This study aimed to determine whether patients with chronic hypertension but no prior heart, kidney, or liver disease had an elevated risk of SMM compared to those without hypertension or hypertensive disorders in pregnancy.
A retrospective cohort analysis was conducted on 263,518 pregnant patients in northern California who received prenatal care before 14 weeks’ gestation and delivered between 2009 and 2019. Patients with preexisting heart, kidney, or liver disease were excluded. The study classified patients into five groups based on their chronic hypertension status and the development of hypertensive disorders during pregnancy. The primary outcome was SMM at delivery hospitalization, measured by CDC criteria. The results showed that preeclampsia developed in 31.5% of patients with chronic hypertension and 4.7% of those without. The highest SMM rates were observed in patients with chronic hypertension and superimposed preeclampsia (898.3 cases per 10,000 births) and those without chronic hypertension but with preeclampsia (934.3 cases per 10,000 births). Compared to normotensive pregnancies, the risk of SMM was nearly five times higher for these groups (aRR 4.97 and 5.12, respectively). Patients with gestational hypertension had an intermediate risk (aRR 1.78), while those with chronic hypertension but no preeclampsia had only a slightly elevated risk (aRR 1.17).
These findings highlight the critical role of preeclampsia prevention in mitigating maternal morbidity, particularly among patients with chronic hypertension. While chronic hypertension alone was not associated with a substantial increase in SMM risk, the development of preeclampsia significantly amplified this risk. Clinically, these results underscore the need for rigorous blood pressure monitoring, early intervention, and potential prophylactic strategies in pregnant patients with chronic hypertension to reduce the incidence of preeclampsia and improve maternal outcomes.
Katrina Thornber, EMJ
Reference
Gunderson EP et al. Severe maternal morbidity associated with chronic hypertension, preeclampsia, and gestational hypertension. JAMA Netw Open. 2025;8(1):e2451406.
