Prevention of Preeclampsia Key to Reducing Severe Maternal Morbidity in Chronic Hypertension: Study Suggests

The study, published in JAMA Network Open, revealed that patients with preeclampsia superimposed on chronic hypertension faced the highest rates of SMM during delivery hospitalization. Similarly, those with preeclampsia but without chronic hypertension experienced significantly elevated SMM rates. These findings highlight the profound impact of preeclampsia, irrespective of its association with chronic hypertension, on maternal health during childbirth.

The researchers note that chronic hypertension and preeclampsia are significant risk factors for maternal and neonatal morbidity and mortality, with severe maternal morbidity encompassing conditions such as heart, kidney, and liver disease. However, existing studies have not excluded patients with preexisting diseases that are commonly associated with SMM, making the risks for uncomplicated chronic hypertension specific to preeclampsia unclear. Erica P. Gunderson, Division of Research, Kaiser Permanente Northern California, Pleasanton, and colleagues aimed to determine the rates of SMM and estimate the relative risks associated with hypertensive disorders of pregnancy, specifically comparing patients with chronic hypertension who do not have preexisting vascular or end-organ diseases to those without chronic hypertension.

For this purpose, the researchers conducted a retrospective cohort study using longitudinal health data from electronic health records of 263,518 pregnant patients within a northern California health system. The cohort included women without pregestational heart, kidney, or liver disease who entered prenatal care by 14 weeks gestation and delivered a singleton stillbirth or live birth between 2009 and 2019. The study analyzed data from February 2022 to March 2024. The researchers assessed SMM rates based on five subgroups of chronic hypertension and hypertensive disorders, estimating relative risks for SMM using modified Poisson regression models adjusted for various covariates.

The study revealed the following findings:

• The study included 263,518 pregnant patients with a mean age of 31.0 years; 249,892 had no chronic hypertension (4.7% developed preeclampsia), and 13,626 had chronic hypertension (31.5% developed superimposed preeclampsia).
• The highest severe maternal morbidity (SMM) rates were observed in the no chronic hypertension with preeclampsia (934.3 cases per 10,000 births) and chronic hypertension with superimposed preeclampsia (898.3 cases per 10,000 births) groups.
• Lower SMM rates were found in the chronic hypertension without preeclampsia (195.1 cases per 10,000 births), gestational hypertension (312.7 cases per 10,000 births), and no chronic hypertension without preeclampsia or gestational hypertension (165.8 cases per 10,000 births) groups.
• Compared to the reference group (no chronic hypertension, no preeclampsia or gestational hypertension), the risks of SMM were significantly higher for the chronic hypertension with superimposed preeclampsia group (aRR, 4.97), no chronic hypertension with preeclampsia group (aRR, 5.12), chronic hypertension without preeclampsia group (aRR, 1.17), and gestational hypertension group (aRR, 1.78).

The study provides valuable evidence, demonstrating that individuals with chronic hypertension who did not develop preeclampsia face only a modestly higher absolute risk of severe maternal morbidity (SMM) compared to those who remain normotensive. Additionally, the findings contribute to the growing body of evidence supporting precision medicine to enhance preeclampsia risk stratification, as recommended by professional organizations.

"Given that preeclampsia is a major contributor to maternal and newborn morbidity and mortality, these results highlight the critical need for effective prevention and management of chronic hypertension before and during pregnancy to reduce morbidity associated with preeclampsia," the researchers concluded.

Reference:

Gunderson EP, Greenberg M, Najem M, et al. Severe Maternal Morbidity Associated With Chronic Hypertension, Preeclampsia, and Gestational Hypertension. JAMA Netw Open. 2025;8(1):e2451406. doi:10.1001/jamanetworkopen.2024.51406