Severe preeclampsia is a dangerous pregnancy complication defined by very high blood pressure combined with signs of organ damage, typically developing after 20 weeks of gestation. It affects roughly 2 to 8% of all pregnancies worldwide and is one of the leading causes of serious illness and death for both mothers and babies. Unlike mild preeclampsia, the severe form can progress rapidly and often requires early delivery, sometimes weeks before the due date.
How It Differs From Mild Preeclampsia
All preeclampsia involves high blood pressure that develops during pregnancy, but the severe form crosses specific thresholds. A diagnosis of severe preeclampsia (sometimes called “preeclampsia with severe features”) requires at least one of the following: a systolic blood pressure of 160 or higher, or a diastolic of 110 or higher, measured on two separate occasions at least four hours apart. But blood pressure alone isn’t the whole picture. Severe preeclampsia can also be diagnosed when organ damage is present, even if blood pressure hasn’t hit those extreme numbers.
The types of organ damage that qualify include a drop in platelet count (the blood cells responsible for clotting), kidney dysfunction, elevated liver enzymes, fluid in the lungs, or neurological symptoms like severe headaches or vision changes. Any one of these findings, combined with elevated blood pressure during pregnancy, can shift a diagnosis from mild to severe.
What Causes It
The root of preeclampsia lies in the placenta. In a healthy pregnancy, the blood vessels that supply the placenta (called spiral arteries) undergo a dramatic transformation early on. They lose much of their muscular wall and widen significantly, turning from narrow, high-resistance tubes into wide, free-flowing channels. This remodeling is what allows enough blood to reach the growing baby.
In preeclampsia, that remodeling fails. The spiral arteries keep much of their muscular wall intact, staying narrow and restricting blood flow to the placenta. The placenta becomes oxygen-starved, and in response, it releases substances into the mother’s bloodstream that interfere with the normal function of blood vessel walls throughout her entire body. This widespread blood vessel dysfunction is what drives up blood pressure and damages the kidneys, liver, brain, and other organs. It also disrupts the balance between factors that promote healthy blood vessel growth and factors that suppress it, tipping the scales toward damage and inflammation.
Symptoms and Warning Signs
Severe preeclampsia sometimes develops without obvious symptoms, which is why blood pressure checks at prenatal visits matter so much. When symptoms do appear, they tend to signal that organs are already under stress.
- Severe headaches that don’t respond to typical pain relief
- Vision changes including blurred vision, light sensitivity, or temporary loss of vision
- Upper belly pain, usually under the ribs on the right side, caused by liver swelling
- Shortness of breath from fluid accumulating in the lungs
- Nausea or vomiting that appears suddenly in the second half of pregnancy
- Sudden swelling of the face and hands, or rapid weight gain over a few days
Any of these symptoms in the second half of pregnancy warrants urgent medical attention. They can appear gradually or come on within hours.
Risks to the Baby
Because preeclampsia restricts blood flow through the placenta, the baby may not receive enough oxygen and nutrients. This can lead to fetal growth restriction, where the baby falls significantly below expected size for gestational age. Growth restriction related to placental problems complicates up to 10% of pregnancies overall and is one of the leading causes of newborn illness and death.
The other major risk is prematurity. When severe preeclampsia develops well before the due date, doctors often need to deliver the baby early to protect the mother’s health. Babies born before 34 weeks face higher rates of breathing problems, feeding difficulties, and longer stays in the neonatal intensive care unit. There is also a risk of placental abruption, where the placenta separates from the uterine wall before delivery, which can be life-threatening for both mother and baby.
HELLP Syndrome
HELLP syndrome is a severe complication that can develop alongside or independent of preeclampsia. The name stands for hemolysis (the destruction of red blood cells), elevated liver enzymes, and low platelet count. It is diagnosed when all three are present: platelet counts drop below 100,000 per microliter, liver enzymes rise to more than double their normal levels, and lab work shows red blood cells are being broken apart in the bloodstream.
Symptoms of HELLP often mimic other conditions, which makes it tricky to catch. Nausea, vomiting, upper right belly pain, headache, and a general feeling of being unwell are the most common signs. HELLP syndrome can escalate quickly and typically requires immediate delivery regardless of how far along the pregnancy is.
How It Is Managed
There is no cure for preeclampsia other than delivering the baby and the placenta. Every treatment decision balances the mother’s safety against the baby’s need for more time to develop.
When severe preeclampsia develops at or after 34 weeks, delivery is typically recommended promptly. Before 34 weeks, doctors may attempt to delay delivery for a short period, sometimes just 48 hours, to administer steroids that help the baby’s lungs mature faster. This delay is only considered when the mother’s condition is stable enough to allow it. If blood pressure becomes uncontrollable, organ damage worsens, or the baby shows signs of distress, delivery happens regardless of gestational age.
Magnesium sulfate is given intravenously to prevent seizures (a condition called eclampsia) during labor and in the hours after delivery. Blood pressure medications are also used to bring dangerously high readings down to safer levels, reducing the risk of stroke. After delivery, preeclampsia usually resolves within days to weeks, though blood pressure monitoring continues in the postpartum period because symptoms can worsen or first appear after the baby is born.
Long-Term Health After Preeclampsia
A history of preeclampsia is now recognized as an independent risk factor for heart disease later in life. A large meta-analysis found that women who had preeclampsia face roughly 2.5 times the risk of coronary heart disease and about 1.8 times the risk of stroke compared to women who had uncomplicated pregnancies, even after accounting for other risk factors like weight and smoking.
This doesn’t mean heart disease is inevitable, but it does mean the years after a preeclamptic pregnancy are an important window for prevention. Maintaining a healthy weight, staying physically active, managing blood pressure, and keeping up with routine cardiovascular screening all become more meaningful. Many cardiologists now consider a history of preeclampsia as seriously as they would a family history of heart disease when assessing a woman’s long-term risk.