Preeclampsia statistics: risks, racial disparities, and what the screening data shows

In my second year of residency, I watched a 31-year-old patient go from a normal blood pressure reading at her 34-week visit to seizures on the labor and delivery floor 72 hours later. Her blood pressure spiked to 190/120. Her liver enzymes tripled overnight. She delivered by emergency cesarean and spent four days in the ICU. Both she and the baby survived, but it was close. That is what preeclampsia can do — move from stable to catastrophic in a matter of days.

Preeclampsia is a pregnancy-specific condition characterized by new-onset hypertension and organ dysfunction, typically appearing after 20 weeks of gestation. It complicates 2% to 8% of pregnancies worldwide, according to the WHO, and remains one of the leading causes of maternal and perinatal death globally. The condition is treatable (delivery is the definitive cure) but when it is missed, mismanaged, or progresses to eclampsia, the consequences can be fatal.

How common is preeclampsia

Globally, the WHO estimates that hypertensive disorders affect 5% to 14% of all pregnancies. Preeclampsia specifically falls in the 2% to 8% range, varying by population, diagnostic criteria, and healthcare access. In low-income countries, where prenatal care is limited, the rate tends toward the higher end of that range and the outcomes are worse.

In the United States, the picture has been getting worse, not better. ACOG's 2020 Practice Bulletin on gestational hypertension and preeclampsia noted that rates of preeclampsia have increased over the past 20 to 25 years. Part of that increase is attributed to rising rates of known risk factors: advanced maternal age, obesity, and chronic hypertension in women of reproductive age. Between 2000 and 2014, the rate of severe preeclampsia roughly doubled.

There are about 3.6 million births per year in the U.S. At a 4% to 5% rate, that translates to approximately 144,000 to 180,000 cases of preeclampsia annually. Not all of these are severe, but every case requires monitoring, and the line between mild and severe can shift rapidly.

Preeclampsia does not only endanger the mother. It is the leading identified cause of medically indicated preterm birth and accounts for about 15% of all preterm deliveries. Babies born prematurely because of maternal preeclampsia face the full spectrum of prematurity-related complications: respiratory distress, intraventricular hemorrhage, necrotizing enterocolitis, and long-term developmental delays.

Who is at highest risk

ACOG identifies several high-risk and moderate-risk factors for preeclampsia. The categorization matters because it determines who should receive aspirin prophylaxis.

High-risk factors (any single one qualifies for aspirin prophylaxis):

• Previous pregnancy with preeclampsia
• Multifetal gestation (twins, triplets)
• Chronic hypertension
• Pregestational diabetes (type 1 or type 2)
• Chronic kidney disease
• Autoimmune disease (systemic lupus erythematosus, antiphospholipid syndrome)

Moderate-risk factors (two or more together qualify for aspirin):

• First pregnancy (nulliparity)
• Maternal age 35 or older
• BMI over 30
• Family history of preeclampsia (mother or sister)
• Previous adverse pregnancy outcome (growth restriction, stillbirth)
• Interpregnancy interval greater than 10 years
• Sociodemographic factors (Black race, low socioeconomic status)

Nulliparity alone carries a significant risk. First pregnancies account for about 75% of preeclampsia cases. The immune system's first encounter with paternal antigens in placental tissue is thought to play a role, which is why preeclampsia risk is often lower in subsequent pregnancies — unless the partner changes, which resets the immunological exposure.

Conditions that already stress the cardiovascular system compound the risk. Women with undiagnosed thyroid disorders, for instance, may enter pregnancy with metabolic imbalances that make blood pressure regulation harder. If you are tracking early pregnancy and wondering whether your symptoms are normal, our implantation bleeding vs. period guide covers how to distinguish early pregnancy signs from other causes.

The racial disparity in preeclampsia

The data on racial disparities in preeclampsia is among the most troubling in maternal health.

Black women in the United States are approximately 60% more likely to develop preeclampsia than white women. But the disparity does not stop at incidence. Black women who develop preeclampsia are more likely to have severe disease, more likely to develop eclampsia, and 3 to 4 times more likely to die from pregnancy-related hypertensive disorders.

A 2019 CDC Vital Signs report by Petersen and colleagues analyzed pregnancy-related deaths from 2011 to 2015 and found that Black women had a pregnancy-related mortality rate of 42.8 deaths per 100,000 live births, compared to 13.0 for white women. Hypertensive disorders were among the leading causes of these deaths, and the racial gap was wider for hypertension-related mortality than for several other causes.

The reasons behind this disparity are not genetic. They are structural. Black women in the U.S. have higher rates of chronic hypertension before pregnancy, partly driven by the cumulative physiological effects of systemic racism — what researchers call "weathering." They are more likely to receive prenatal care at under-resourced facilities. They are more likely to have their symptoms minimized. And they are less likely to receive timely escalation when their condition deteriorates.

A 2022 study published in Obstetrics & Gynecology found that Black women presenting to triage with hypertensive symptoms waited longer before evaluation and were less likely to receive magnesium sulfate prophylaxis before their blood pressure crossed the threshold for severe preeclampsia. These are not subtle differences. They are measurable gaps in standard-of-care delivery that contribute directly to excess mortality.

What preeclampsia does to the body

Preeclampsia is fundamentally a disease of the placental vasculature. In normal pregnancy, the spiral arteries that supply blood to the placenta are remodeled to become wider, lower-resistance vessels. In preeclampsia, that remodeling is incomplete. The result is a placenta that is inadequately perfused, which triggers a cascade of systemic effects.

The dysfunctional placenta releases factors into the maternal bloodstream — including soluble fms-like tyrosine kinase 1 (sFlt-1), which binds and neutralizes vascular endothelial growth factor (VEGF) and placental growth factor (PlGF). The net effect is widespread endothelial dysfunction: the blood vessel lining throughout the mother's body becomes damaged and inflamed.

That endothelial damage produces the clinical features of preeclampsia:

• Hypertension (the blood vessels constrict)
• Proteinuria (the kidney's filtering apparatus leaks protein)
• Edema (fluid leaks from damaged blood vessels into tissues)
• Liver damage (in severe cases, causing elevated liver enzymes and right upper quadrant pain)
• Thrombocytopenia (low platelets, because they are consumed in repairing damaged vessel walls)
• Cerebral edema (which can cause headache, visual changes, and seizures)

The severity of preeclampsia exists on a spectrum. "Preeclampsia without severe features" involves blood pressure of 140/90 or higher with proteinuria but no evidence of end-organ damage. "Preeclampsia with severe features" includes any of: blood pressure 160/110 or higher, thrombocytopenia, impaired liver function, renal insufficiency, pulmonary edema, or cerebral/visual symptoms. The distinction drives management — mild preeclampsia at term can be managed with delivery, while severe preeclampsia may require emergent delivery regardless of gestational age.

Eclampsia, HELLP, and maternal mortality

Eclampsia (the occurrence of seizures in a preeclamptic patient) is the most feared acute complication. It occurs in approximately 1 in 200 preeclampsia cases (0.5%) in developed countries with good prenatal care. In regions with limited access to obstetric services, the rate is significantly higher.

Magnesium sulfate, administered intravenously, reduces the risk of eclamptic seizures by approximately 50% in women with severe preeclampsia, based on the landmark Magpie Trial (Lancet, 2002), which enrolled over 10,000 women across 33 countries. It remains one of the most cost-effective interventions in obstetrics.

HELLP syndrome (Hemolysis, Elevated Liver enzymes, Low Platelets) is a severe variant that complicates about 10% to 20% of severe preeclampsia cases. It can cause liver rupture, disseminated intravascular coagulation (DIC), and maternal death. HELLP can also develop without preceding hypertension or proteinuria, which makes it particularly dangerous because it may not be recognized as a preeclampsia-spectrum disorder until the patient is critically ill.

Hypertensive disorders of pregnancy (preeclampsia, eclampsia, and chronic hypertension) account for approximately 7.4% of pregnancy-related deaths in the United States, according to Creanga and colleagues' analysis of 2011–2013 data in Obstetrics & Gynecology. The WHO estimates that hypertensive disorders cause 14% of maternal deaths globally, with the burden concentrated in low- and middle-income countries. The global toll is approximately 76,000 maternal deaths and 500,000 fetal or neonatal deaths per year.

Screening and early detection

Blood pressure measurement at every prenatal visit is the cornerstone of preeclampsia screening. It is simple, inexpensive, and effective. But blood pressure alone does not predict who will develop preeclampsia before symptoms appear.

ACOG recommends that all pregnant women be assessed for preeclampsia risk factors at their first prenatal visit, using the high-risk and moderate-risk factor list described above. Women who meet the criteria should begin aspirin prophylaxis before 16 weeks.

More sophisticated screening approaches are being developed. First-trimester screening algorithms that combine maternal risk factors with uterine artery Doppler measurements, mean arterial pressure, and serum biomarkers (PAPP-A and PlGF) can identify women at high risk for preterm preeclampsia with a detection rate of about 75% at a 10% false-positive rate. The Fetal Medicine Foundation algorithm, developed by Kypros Nicolaides' group, is the best validated of these. It was used in the ASPRE trial to select high-risk women for aspirin prophylaxis.

In clinical practice in the United States, first-trimester combined screening for preeclampsia is not yet standard. Most providers rely on the ACOG risk-factor approach, which is simpler but less precise. Women identified as high-risk should expect closer monitoring: more frequent blood pressure checks, urine protein screening, and attention to symptoms like headache, visual changes, and epigastric pain.

If you are navigating early pregnancy and want to understand your risk timeline, our period calculator and ovulation calculator can help establish your gestational dates — accurate dating matters for preeclampsia monitoring because the condition's risk profile changes significantly by gestational age.

Low-dose aspirin prophylaxis

The evidence for low-dose aspirin in preventing preeclampsia is strong and specific.

The ASPRE trial (Rolnik et al., 2017), published in the New England Journal of Medicine, randomized 1,776 women identified as high-risk for preterm preeclampsia to receive either aspirin 150 mg nightly or placebo, starting between 11 and 14 weeks of gestation. The result: aspirin reduced the incidence of preterm preeclampsia (delivery before 37 weeks) by 62%. The effect on term preeclampsia was not significant, suggesting that aspirin primarily benefits the most dangerous early-onset form of the disease.

Based on this and earlier evidence, the USPSTF published a recommendation in 2021 (reaffirming earlier guidance) that women at high risk for preeclampsia should take low-dose aspirin (81 mg/day in the U.S., where 81 mg is the standard low-dose formulation) starting at 12 to 16 weeks of pregnancy. ACOG aligns with this recommendation.

Timing matters. The benefit of aspirin is thought to come from its effect on trophoblast invasion and spiral artery remodeling, processes that are most active in the first and early second trimester. Starting aspirin after 16 weeks appears to have less benefit. Starting before 12 weeks has not been shown to add additional benefit and may theoretically increase first-trimester bleeding, though the data on this is limited.

Compliance is important. The aspirin must be taken nightly (some evidence suggests bedtime dosing is more effective for blood pressure reduction). Women who stop early or take it inconsistently do not get the full protective effect.

Despite clear guidelines, aspirin prophylaxis remains underused. Studies have found that only 40% to 60% of eligible women receive it, often because risk assessment is not performed early enough in prenatal care or because providers are unaware of the updated recommendations.

Long-term cardiovascular risk after preeclampsia

The most important thing many women do not know about preeclampsia is this: it does not end when the pregnancy ends.

A 2007 systematic review and meta-analysis by Bellamy and colleagues, published in the BMJ, analyzed 25 studies involving over 3 million women. The findings: women who had preeclampsia had approximately double the risk of developing ischemic heart disease (relative risk 2.16), stroke (relative risk 1.81), and venous thromboembolism (relative risk 1.79) in the years and decades following their pregnancy. The risk of developing chronic hypertension was nearly 4 times higher (relative risk 3.70).

These are not abstract future risks. The elevated cardiovascular risk begins early. Shahul and colleagues published data in Circulation: Cardiovascular Imaging in 2015 showing that women who had preeclampsia had measurable subclinical left ventricular dysfunction at one year postpartum, even when they were asymptomatic and their blood pressure had normalized.

The American Heart Association recognized preeclampsia as a cardiovascular risk factor in its 2011 guidelines for the prevention of cardiovascular disease in women. Yet follow-up data suggests that most women who have had preeclampsia are not receiving the cardiovascular monitoring they should. A 2020 study found that fewer than 50% of women with a history of preeclampsia had their blood pressure checked within a year of delivery.

If you have had preeclampsia, the practical steps are clear:

• Annual blood pressure monitoring, starting immediately postpartum
• Lipid panel and fasting glucose screening, starting within 6 to 12 months
• Attention to modifiable cardiovascular risk factors: smoking, obesity, physical inactivity, and diet
• Inform every healthcare provider you see that you had preeclampsia — it changes your risk profile permanently

Our health resources page has links to cardiovascular risk tools and lifestyle modification guides that may be helpful for long-term planning after a preeclamptic pregnancy.

Frequently asked questions about preeclampsia

How common is preeclampsia?

Preeclampsia affects 2% to 8% of pregnancies worldwide, according to the WHO. In the United States, the rate is approximately 4% to 5%, which translates to roughly 144,000 to 180,000 cases per year. Rates have been increasing over the past two decades, partly due to rising rates of maternal obesity, advanced maternal age, and chronic hypertension.

Are Black women more likely to get preeclampsia?

Yes. Black women in the United States are approximately 60% more likely to develop preeclampsia than white women. They are also 3 to 4 times more likely to die from pregnancy-related hypertensive disorders, according to a 2019 CDC Vital Signs report. The disparity is driven by higher rates of underlying chronic hypertension, structural inequities in healthcare access, and documented differences in the quality and timeliness of clinical care.

Does aspirin prevent preeclampsia?

Low-dose aspirin (81 mg daily in the U.S.) started before 16 weeks of pregnancy reduces the risk of preterm preeclampsia by approximately 62%, based on the ASPRE trial published in the New England Journal of Medicine (Rolnik et al., 2017). The USPSTF and ACOG recommend aspirin prophylaxis for women identified as high-risk based on clinical factors such as prior preeclampsia, chronic hypertension, diabetes, or multifetal pregnancy.

Can preeclampsia cause long-term health problems?

Yes. A meta-analysis by Bellamy et al. (2007) in the BMJ found that women who had preeclampsia had approximately double the long-term risk of heart disease and stroke, and nearly 4 times the risk of developing chronic hypertension. The American Heart Association recognizes preeclampsia as a cardiovascular risk factor. Women with a preeclampsia history should receive annual blood pressure monitoring and cardiovascular screening.

What are the warning signs of preeclampsia?

Key warning signs include new-onset severe headaches that do not respond to medication, visual changes (blurring, flashing lights, seeing spots), upper abdominal pain (especially under the right ribs), sudden swelling of the face or hands, and sudden weight gain from fluid retention. Blood pressure of 140/90 or higher after 20 weeks of pregnancy warrants immediate evaluation. Some women with preeclampsia have no symptoms, which is why blood pressure monitoring at every prenatal visit is essential.

Is preeclampsia hereditary?

Preeclampsia has a genetic component. Women whose mothers or sisters had preeclampsia have approximately 2 to 3 times the risk compared to women without a family history. The genetics are complex, involving multiple genes related to immune function, vascular development, and placental biology. A family history of preeclampsia is one of the moderate risk factors that, combined with another moderate factor, qualifies a woman for aspirin prophylaxis per ACOG guidelines.