Preeclampsia is a serious pregnancy complication defined by new high blood pressure and signs of organ damage, most often affecting the kidneys and liver. It develops after 20 weeks of pregnancy and affects roughly 1 in 25 pregnancies in the United States. Without monitoring and treatment, it can progress to life-threatening seizures, organ failure, or stroke for the mother, and growth restriction or premature birth for the baby.
What Happens in the Body
Preeclampsia starts with a problem in the placenta. Normally, the placenta builds a rich network of blood vessels that tap into the mother’s blood supply to nourish the baby. In preeclampsia, those blood vessels don’t develop properly. The placenta gets less blood flow than it needs, and the resulting oxygen shortage causes tissue damage.
That damaged placental tissue releases substances into the mother’s bloodstream that interfere with blood vessel function throughout her body. Specifically, the placenta overproduces proteins that block the growth of new blood vessels and ramp up inflammation. This triggers widespread damage to the lining of blood vessels, a condition called endothelial dysfunction. Once the blood vessel lining is compromised, the effects cascade: blood pressure rises, the kidneys start leaking protein, the liver can become inflamed, and fluid can accumulate in the lungs or brain. The disease isn’t just high blood pressure during pregnancy. It’s a whole-body vascular crisis triggered by a malfunctioning placenta.
When It Develops
Preeclampsia typically appears after 20 weeks of pregnancy. When it shows up before 34 weeks, it’s classified as early-onset preeclampsia, which tends to be more severe because the baby is further from being ready for delivery. Late-onset preeclampsia, appearing at 34 weeks or later, is more common and generally carries a better prognosis simply because the baby is closer to full term.
The condition can also develop after delivery. Most cases of postpartum preeclampsia show up within 48 hours of childbirth, but it can appear as late as six weeks after delivery. This catches many new parents off guard because they assume the risk ends once the baby is born.
Who Is at Higher Risk
Several factors raise the likelihood of developing preeclampsia. A first pregnancy is one of the strongest risk factors, as is a personal history of preeclampsia in a previous pregnancy. The CDC lists these additional risk factors:
- Chronic high blood pressure or kidney disease before pregnancy
- Type 1 or type 2 diabetes
- BMI of 35 or higher
- Age 40 or older
- Family history of preeclampsia (a parent or sibling who had it)
- In vitro fertilization
- Thrombophilia (a blood-clotting disorder)
- Long gap between pregnancies
Having one of these factors doesn’t mean you’ll develop preeclampsia, but having multiple factors increases the odds significantly. For people considered high risk, the U.S. Preventive Services Task Force recommends taking low-dose aspirin (81 mg daily) starting after 12 weeks of pregnancy. This is the single most evidence-backed prevention strategy available.
Symptoms to Recognize
Early preeclampsia often produces no obvious symptoms, which is why blood pressure checks at every prenatal visit matter so much. As the condition progresses, it can produce warning signs that range from subtle to alarming.
Protein leaking into the urine is one of the hallmark findings, but you won’t notice that on your own. What you might notice: sudden swelling in the face or hands, rapid weight gain over a few days (from fluid retention), and persistent headaches that don’t respond to typical pain relief. More serious symptoms include changes in vision like blurriness, light sensitivity, or temporary vision loss. Pain in the upper right abdomen, just under the ribs, signals liver involvement. Shortness of breath can mean fluid is building up in the lungs. Nausea or vomiting in the second half of pregnancy, when morning sickness has long passed, is another red flag.
The Mayo Clinic specifically warns that severe headaches, vision problems, mental confusion, or altered behavior can be signs that seizures (eclampsia) are imminent. These symptoms warrant emergency care, not a next-day phone call.
How It’s Diagnosed
Diagnosis starts with blood pressure readings. Preeclampsia is suspected when a previously normal blood pressure rises to 140/90 or higher on two separate readings. To confirm organ involvement, providers check for protein in the urine, either through a single urine sample or a 24-hour urine collection. A protein-to-creatinine ratio above 0.3 in a single sample is considered significant, as recommended by the American College of Obstetricians and Gynecologists.
Blood tests round out the picture: liver enzymes, platelet counts, and kidney function markers help determine how much organ damage is occurring and whether the condition has progressed to a more dangerous stage. Some medical centers now use a blood test measuring the ratio of two placental proteins to help predict whether preeclampsia will worsen. In a large study called PROGNOSIS, a low ratio was able to rule out preeclampsia developing within one week with 99.3% accuracy, giving providers a useful window for safe monitoring.
Severe Features and HELLP Syndrome
Preeclampsia exists on a spectrum. In its severe form, blood pressure climbs to 160/110 or higher, and organ damage accelerates. The most dangerous variant is HELLP syndrome, a name describing its three defining features: hemolysis (red blood cells breaking apart), elevated liver enzymes, and low platelet count. Platelets drop below 100,000 per microliter, liver enzymes spike, and fragments of destroyed red blood cells show up on blood smears.
HELLP syndrome can develop rapidly, sometimes before blood pressure is dramatically elevated, which makes it particularly dangerous. Symptoms often mimic other conditions: upper abdominal pain, nausea, and general malaise that could be mistaken for a stomach bug. It requires immediate hospitalization because it can lead to liver rupture, stroke, or placental abruption (the placenta separating from the uterine wall).
Treatment and Delivery
Delivery is the only cure for preeclampsia. Once the placenta is removed, the disease process stops. The central challenge is timing: delivering too early puts the baby at risk from prematurity, while waiting too long puts the mother at risk from worsening organ damage.
For mild preeclampsia diagnosed before 37 weeks, the approach is usually close monitoring with frequent blood pressure checks, blood work, and fetal assessments. If the condition stays stable, providers aim to continue the pregnancy as long as safely possible. For severe preeclampsia or HELLP syndrome, delivery is typically recommended regardless of gestational age once the mother is stabilized.
Magnesium sulfate is given intravenously during labor and for 24 to 48 hours afterward to prevent seizures. It has been used for this purpose for over a century and remains the standard of care. Blood pressure medications are used to keep dangerously high readings in a safe range during this period.
What Recovery Looks Like
For most people, blood pressure begins to normalize within days to weeks after delivery. Some experience elevated blood pressure for up to 12 weeks postpartum, and a small percentage develop chronic hypertension that persists long term. The weeks after delivery require continued blood pressure monitoring, especially since postpartum preeclampsia can still emerge.
Having preeclampsia also changes your long-term health profile. It roughly doubles the lifetime risk of cardiovascular disease, including heart attack and stroke, later in life. This doesn’t mean these outcomes are inevitable, but it does mean that regular cardiovascular screening, maintaining a healthy weight, and managing blood pressure become more important in the years and decades after a preeclamptic pregnancy.