Preeclampsia

Contents

1. Two numbers define the threshold
2. A disorder that begins in the placenta
3. An old disease with an old name
4. It is common and becoming more so
5. Risk factors are many and imprecise
6. Symptoms are easy to mistake
7. Delivery remains the cure
8. The risk continues after birth

Preeclampsia is among the conditions watched for in the pregnancies, ordinary and complicated alike, that Candace Cooley has managed as an obstetrician, and its definition starts with a measurement in millimeters of mercury, written mm Hg, the unit in which public health agencies set the blood pressure thresholds for pregnancy. Two numbers are recorded at each reading, and in pregnancy the line that matters is 140 over 90.

Two numbers define the threshold

The Centers for Disease Control and Prevention defines high blood pressure in a pregnant woman as a reading of 140/90 mm Hg or higher on two occasions at least four hours apart, and severe high blood pressure as 160/110 mm Hg on two or more occasions. Preeclampsia is diagnosed when a woman whose pressure was normal develops high blood pressure after 20 weeks of pregnancy together with protein in the urine or other problems; women with chronic hypertension can develop it too. Eclampsia, its most dangerous turn, adds seizures with no other cause and is a medical emergency.⁴

A disorder that begins in the placenta

The raised pressure is the visible sign of a deeper problem. In a 2026 report, NPR quoted a South African obstetrician describing preeclampsia as the placenta signaling that it is short of oxygen and pushing the mother’s blood pressure up to get more blood.¹ Researchers in a 2025 Brazilian study describe the early onset form as the more severe variant, possibly the result of placental dysfunction.⁶ CNN reported in 2024 on a commercial first trimester risk test that measures placental proteins, on the reasoning that low levels may mean a placenta developing and working poorly.¹⁰

Figure

Pressure disorders of pregnancy compared

	Gestational hypertension	Preeclampsia
Blood pressure before pregnancy	Normal	Normal, or already high in chronic hypertension
What is found	High blood pressure alone	High blood pressure with protein in the urine or other problems
Timing	During pregnancy	After 20 weeks, or after birth
Can progress to	Severe high blood pressure	Eclampsia, with seizures

An old disease with an old name

The condition has a long written history. A 2017 column in MDedge traces descriptions to the time of Hippocrates in the fourth and fifth centuries BC, notes that it was not formally classed as a pressure disorder specific to pregnancy until the late 1800s, and calls its underlying causes still largely unknown.³ A 2008 CNN report recalled its older name, toxemia, and noted that most women with the condition go on to deliver healthy babies and recover well, while untreated disease can progress to seizures and stroke.⁹

It is common and becoming more so

The CDC estimates that preeclampsia occurs in about 2 to 8 percent of pregnancies and counts it among the leading causes of death related to pregnancy; pressure disorders of all kinds affect 5 to 10 percent of pregnant women, a rise of a quarter over two decades.⁴ A CDC analysis published in 2022 found such disorders in a rising share of delivery hospitalizations and documented in nearly a third of the women who died during them.⁵ NPR reported in 2024 that rates of new and chronic high blood pressure among pregnant women had roughly doubled since 2007, partly because more testing finds them.⁸

Figure

Pressure disorders at delivery, 2017 to 2019

of delivery hospitalizations with a pressure disorder in 2017

13.3%

in 2019

15.9%

of deaths during delivery hospitalization with one documented

31.6%

Risk factors are many and imprecise

The CDC lists a first birth, preeclampsia in an earlier pregnancy, chronic high blood pressure or kidney disease, a clotting disorder, twins or more, a family history, diabetes, obesity, lupus and age over 40.⁴ These factors predict less than their length suggests. When researchers applied the national screening categories to more than 5,600 pregnancies, STAT reported in 2025, nearly nine in ten women counted as at risk, yet only about one in ten of those in the moderate group and fewer than a quarter in the high group went on to develop the disease. Of the moderate factors, only a first birth showed a consistent link. The same report puts the disease at about 4 percent of American pregnancies.²

Symptoms are easy to mistake

The CDC’s list of symptoms includes a headache that will not go away, blurred vision or spots, pain in the upper abdomen, nausea or vomiting, a puffy face or swollen hands, sudden weight gain and trouble breathing, and it stresses that some women have no symptoms at all.⁴ Several of these overlap with an ordinary late pregnancy, a point the 2008 CNN report made: a doctor tells them apart by checking pressure and measuring protein in the urine.⁹ A 2025 survey of 122 pregnant women in Saudi Arabia found only moderate knowledge of the disease and cited earlier work showing that first time mothers often struggle to separate normal symptoms from warning ones.⁷ These symptoms appear on the broader list of maternal warning signs.

Delivery remains the cure

There is still no cure but birth. The 2024 NPR report notes that delivery is the typical cure, and that medicines can prevent seizures and speed fetal maturity when an early birth is needed; it adds that ACOG lowered its threshold for treating high pressure in pregnant and postpartum patients in 2022.⁸ In South Africa, the 2026 NPR report found researchers testing a candidate medicine on women already scheduled for early delivery; at higher amounts it brought their pressure down and seemed to increase flow to the womb, though an outside specialist called the trial small and in need of a broader population. Ordinary pressure medicines carry a drawback the trial hoped to avoid, since lowering the mother’s pressure can also cut blood supply to the baby.¹ Care for women at highest risk often involves maternal fetal medicine subspecialists.

The risk continues after birth

Preeclampsia does not always end with delivery. The CDC notes that it can first appear after birth, usually within 48 hours but up to six weeks later, even in women who had no sign of it during pregnancy, and that high pressure in pregnancy raises the risk of stroke after delivery.⁴ In the Brazilian study, 15 of 24 women were still hypertensive three months after birth, and the authors cite evidence that the risk of chronic hypertension stays two to four times higher for a decade or two.⁶

Figure

Blood pressure after preeclampsia

still hypertensive three months after birth

62.5%

the risk of persistent hypertension after early onset disease

2.36 times

the risk of chronic hypertension 10 to 20 years later

2 to 4 times

The evidence is strongest at the two ends of the subject. Delivery reliably ends the disease, and the CDC states that low dose aspirin, taken at the right time, has been shown to reduce the risk of preeclampsia in some women at higher risk.⁴ Between those points the record is thinner: the 2024 CNN report quoted ACOG as saying it was unclear how well the new first trimester test predicts risk.¹⁰ Whether any one woman needs closer monitoring or preventive treatment is a decision she makes with her own clinician.