Preventing preeclampsia may lower maternal health risks linked to hypertension

Preventing preeclampsia may lower maternal health risks linked to hypertension | Image Credit: © Sukjai Photo - © Sukjai Photo - stock.adobe.com.

Preeclampsia prevention may help reduce the risk of severe maternal morbidity (SMM) in pregnant women with uncomplicated chronic hypertension, according to a recent study published in JAMA Network Open.¹

Approximately 3% to 5% of pregnancies are impacted by hypertension, which has been linked to increased morbidity and mortality among mothers and infants. These risks are significantly increased among patients with hypertensive disorders of pregnancy and pregestational comorbidities.²

According to investigators, “the risk of maternal morbidity outcomes for patients with chronic hypertension, complicated or not by preeclampsia and in the absence of other preexisting disease, remains unclear.”¹ Therefore, a cohort study was conducted to assess SMM rates linked to chronic hypertension and hypertensive disorders of pregnancy.

Data was obtained from the Kaiser Permanente Northern California (KPNC), a health care system encompassing over 4.6 million individuals across more than 255 medical facilities. Clinical outpatient blood pressure (BP) measurements, medical diagnoses, pregnancy course and outcomes, sociodemographic characteristics, and more are included in the KPNC databases.

Participants included pregnant individuals without prepregnancy comorbidities delivering a singleton stillbirth or live birth neonate, having entered the KPNC no later than 14 weeks’ gestation. Centers for Disease Control and Prevention criteria was used to determine SMM presence based on at least 1 of 21 indicators.

KPNC local-use procedure codes for ventilation, cardiac rhythm, hysterectomy, and temporary tracheostomy were also obtained. SMM rates were calculated as cases per 10,000 births.

Prepregnancy chronic hypertension was defined as hypertension at up to 2 years before conception. Chronic hypertension from week 0 to week 20 of gestation was determined through stage 2 BP elevations on 2 different days or from International Classification of Diseases, Ninth Revision (ICD-9) or ICD-10 codes.

Systolic blood pressure of 140 mm Hg or greater or diastolic BP of 90 mm Hg or greater indicated hypertensive disorders of pregnancy. These conditions were classified as preeclampsia or gestational hypertension.

Pregnancy hypertensive conditions included chronic hypertension with superimposed preeclampsia, chronic hypertension without preeclampsia, preeclampsia without chronic hypertension, and gestational hypertension. Chronic hypertension status and hypertensive disorders developed during pregnancy were reported as 2 separate variables.

There were 263,518 pregnant patients included in the analysis, 5.2% of whom presented with chronic hypertension. Of these patients, 31.5% developed superimposed preeclampsia. In comparison, preeclampsia was reported in 4.7% of patients without chronic hypertension, gestational hypertension in 4.6%, and neither in 90.7%.

The overall SMM rate was 219.6 per 10,000 births. For patients with chronic hypertension, this rate was increased 2-fold at 416.9 per 10,000 births, compared to 208.8 among those without chronic hypertension when not considering preeclampsia or gestational hypertension.

Patients with preeclampsia reported the highest SMM rates, at 898.3 for those with chronic hypertension with superimposed preeclampsia and 934.3 for those with preeclampsia and no chronic hypertension. In comparison, the SMM rate was 195.1 per 10,000 births among patients with chronic hypertension and no preeclampsia.

This was similar to the reference group’s rate of 165.8, but significantly lower than the gestational hypertension group’s rate of 312.7. Overall, adjusted relative risks (aRRs) of SMM for chronic hypertension vs no chronic hypertension, any preeclampsia, and gestational hypertension vs no preeclampsia or gestational hypertension were 1.03, 5.49, and 1.87, respectively.

An aRR for SMM of 4.97 was reported for chronic hypertension with superimposed preeclampsia and 5.12 for preeclampsia with no chronic hypertension when compared to no chronic hypertension, preeclampsia, or gestational hypertension. For chronic hypertension with no preeclampsia and gestational hypertension, the aRRs were 1.17 and 1.78, respectively.

These results indicated preeclampsia as the source of nearly all excess SMM risk linked to chronic hypertension. Investigators concluded there is an “urgency of prevention and control of chronic hypertension before and during pregnancy as an important strategy to mitigate morbidity due to preeclampsia in pregnancy.”

References

1. 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
2. Fink DA, Kilday D, Cao Z,et al. Trends in maternal mortality and severe maternal morbidity during delivery-related hospitalizations in the United States, 2008 to 2021.JAMA Netw Open. 2023;6(6):e2317641. doi:10.1001/jamanetworkopen.2023.17641