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Risk factors for preeclampsia

For preeclampsia, multifetal gestation was the most common high-risk factor among pregnant patients who gave birth in the United States in 2019.

The retrospective cohort study in JAMA Network Open also found that low socioeconomic status was the most frequent moderate-risk factor.1

The study assessed risk factors among pregnant women taking recommended prophylactic low-dose aspirin (LDA), which is 1 of the few evidence-based interventions for preventing preeclampsia and which the US Preventive Services Task Force (USPSTF) embraces.

“Current guidelines recommend LDA based on the presence of risk factors for preeclampsia, but the population-based prevalence of these factors is unknown,” wrote the study authors.

Birth certificate data for the 2019 calendar year from the National Center for Health Statistics was used to determine the pervasiveness of pregnant individuals with moderate to high-risk factors for preeclampsia and pregnancy-related hypertension rates.

The standard birth certificate records 3 of the 6 high-risk factors for which LDA is definitively recommended: multifetal gestation, pregestational diabetes, and chronic hypertension.

The remaining 3 high-risk factors are not recorded in birth records: preeclampsia in a prior pregnancy, renal disease, and autoimmune disease.

Among the 3,695,019 recorded deliveries in 2019 (mean age of the cohort 29.1 years), 528,778 deliveries had no risk factors, while 4.5% of deliveries had at least 1 high-risk factor, and 81.1% had 1 or more moderate-risk factors for preeclampsia.

Multifetal gestation occurred in 3.4% of pregnancies and low socioeconomic status in 46.9% of mothers.

The investigators relied on Medicaid as the primary payer and participation in the women, infant, and children nutritional supplement program as the 2 markers of low socioeconomic status.

The 2 other high-risk factors for preeclampsia were pregestational diabetes and chronic hypertension.

The 5 other moderate risk factors were nulliparity; a body mass index (BMI) greater than 30; African American race; a maternal age 35 years or older; and an interval exceeding 10 years since last birth.

Excluding the births with documented high-risk factors, 35.2% of births had a single moderate-risk factor and 45.8% had 2 or more moderate-risk factors.

The second and third most common moderate-risk factors were nulliparity (30.2%) and obesity (27.4%).

Among individuals with at least 2 moderate-risk factors, low socioeconomic status was present in 69.4% of cases.

The incidence of pregnancy-related hypertension also increased with the number of moderate-risk factors. For instance, birth records meeting 2021 USPSTF criteria to definitively recommend LDA represented 65.3% of cases of pregnancy-related hypertension, whereas records with only a single moderate-risk factor accounted for an additional 27% of cases.

The absolute number of gestational hypertension cases was similar among patients with no risk factors and those with at least 1 high-risk factor: 7.7% vs 8.4%, respectively.

The 2021 guidelines from USPSTF suggest considering or recommend LDA in 92.3% of pregnancies diagnosed with pregnancy-related hypertension.

Because LDA is most effective when started prior to 6 weeks gestation, the study examined the frequency of patients meeting LDA criteria who initiated prenatal care by 16 weeks gestation.

Based on 2021 guideline criteria of a single high risk or moderate-risk factors for preeclampsia, 85.7% of the study cohort was eligible for LDA.

Study data supports the 2021 guidelines, which includes in-vitro conception as a moderate-risk factor. The authors also advocate further simplified guidelines to recommend LDA to patients with any single moderate-risk factor.



Wheeler SM, Myers SO, Swamy GK, et al. Estimated prevalence of risk factors for preeclampsia among individuals giving birth in the US in 2019. Published online January 4, 2022. JAMA Netw Open. 2022;5(1). doi:10.1001/jamanetworkopen.2021.42343