Preeclampsia is a serious pregnancy complication that affects both mother and baby, potentially damaging the mother’s organs while restricting the baby’s growth and oxygen supply. It develops after 20 weeks of pregnancy and is defined by new high blood pressure (140/90 mmHg or higher) along with protein in the urine or signs of organ damage. The effects range from mild and manageable to life-threatening, depending on severity and how early in pregnancy it appears.
What Happens in the Placenta
Preeclampsia begins with a problem in the placenta. Normally, blood vessels in the uterus remodel early in pregnancy to deliver a rich blood supply to the growing baby. In preeclampsia, this remodeling fails. The placenta doesn’t get enough blood flow, becomes oxygen-starved, and starts releasing inflammatory and toxic signals into the mother’s bloodstream. Those signals damage the lining of blood vessels throughout the mother’s body, which is why preeclampsia can affect so many different organs at once.
How Preeclampsia Affects the Mother
The most immediate effect is high blood pressure, but the damage goes well beyond that. The widespread blood vessel dysfunction can harm the kidneys, liver, and brain. Severe preeclampsia, defined by blood pressure reaching 160/110 mmHg or higher on repeated readings, brings symptoms like intense headaches, visual disturbances (blurred vision, seeing spots), and pain in the upper abdomen near the ribs.
One of the most dangerous complications is HELLP syndrome, where red blood cells break apart, liver enzymes spike, and platelet counts drop. HELLP can develop rapidly and requires emergency delivery. The kidneys can also begin failing, leaking large amounts of protein and losing their ability to filter waste. In rare cases, preeclampsia progresses to eclampsia, causing seizures.
Placental abruption, where the placenta tears away from the uterine wall before delivery, is another serious risk. Women with mild preeclampsia face roughly double the risk of abruption compared to women with normal blood pressure. With severe preeclampsia, that risk jumps to more than five times higher. Among women with preeclampsia who deliver before 28 weeks, nearly 9% experience an abruption.
How Preeclampsia Affects the Baby
Because the placenta isn’t functioning properly, the baby receives less oxygen and fewer nutrients than it needs. The body adapts by redirecting blood flow to the most critical organs, especially the brain, at the expense of everything else. This survival response, sometimes called “brain sparing,” slows the baby’s overall growth. Doctors refer to this as fetal growth restriction, and it can appear in different patterns. When the placenta fails early, the baby may be uniformly small. When the problem develops later, the baby’s head may measure normally while the abdomen lags behind, reflecting less stored fat and liver growth.
The other major risk to the baby is preterm birth. Delivery is the only cure for preeclampsia, and when the mother’s condition becomes dangerous, the baby must be delivered early regardless of gestational age. Babies born to mothers with preeclampsia at 35 or 36 weeks are admitted to the neonatal intensive care unit (NICU) at significantly higher rates than babies born at the same age from uncomplicated pregnancies. At 35 weeks, roughly 57% of babies from hypertensive pregnancies needed NICU care compared to about 35% of those from normotensive pregnancies. Even at 37 weeks, which is considered early term, NICU admission rates were about three times higher (26% versus 9%), and hospital stays averaged nearly twice as long.
Babies born from preeclamptic pregnancies are also far more likely to be small for their gestational age. At 36 weeks, about one-third of babies from hypertensive pregnancies fell into this category, compared to roughly 12% from uncomplicated pregnancies.
Long-Term Heart and Metabolic Risks for the Mother
Preeclampsia isn’t just a pregnancy problem. It signals a significantly higher risk of cardiovascular disease for the rest of the mother’s life. A large meta-analysis found that women who had preeclampsia face more than four times the risk of heart failure later in life, two and a half times the risk of coronary heart disease, roughly double the risk of dying from cardiovascular disease, and about 1.8 times the risk of stroke. These numbers held even after accounting for other risk factors like obesity and smoking.
The risk of developing chronic high blood pressure after pregnancy is about three times higher, and the risk of type 2 diabetes roughly doubles. Researchers aren’t entirely sure whether preeclampsia causes these problems directly or whether it reveals an underlying vulnerability that was already there. Either way, the pattern is clear enough that major medical organizations now consider a history of preeclampsia a significant cardiovascular risk factor, on par with traditional warning signs like high cholesterol.
Long-Term Health Effects on the Child
Children born from preeclamptic pregnancies carry their own set of elevated risks, extending well into adulthood. Those born at term to mothers with preeclampsia have a 50% to 60% higher incidence of endocrine and metabolic diseases, including conditions related to blood sugar regulation and cholesterol.
The neurodevelopmental effects are particularly notable. Multiple meta-analyses have found that children exposed to preeclampsia in the womb have a 30% to 50% higher risk of autism spectrum disorder and about a 30% higher risk of ADHD compared to unexposed children. The risk of schizophrenia is elevated by roughly 30% to 40% in most studies, though some research puts it even higher. Children exposed to early or severe preeclampsia may face up to four times the risk of intellectual disability. Population-based studies from Iceland found lower math scores at ages 9, 12, and 15 in children whose mothers had preeclampsia.
It’s worth noting that many of these risks are modest in absolute terms. A 30% increase over a small baseline risk still means the vast majority of children develop normally. But the pattern across so many studies and outcomes suggests that the disrupted placental environment leaves a lasting mark on fetal development, particularly on the brain and metabolic systems.
Prevention and Risk Reduction
For women identified as high risk, low-dose aspirin (81 mg daily) is the primary preventive tool available. The U.S. Preventive Services Task Force recommends starting it after 12 weeks of pregnancy, and the American College of Obstetricians and Gynecologists specifies that the ideal window is before 16 weeks, continuing daily until delivery. High-risk factors include a previous pregnancy with preeclampsia, carrying multiples, chronic high blood pressure, diabetes, kidney disease, or autoimmune conditions.
Aspirin works by reducing inflammation and improving blood flow to the placenta during the critical early weeks when those spiral arteries are supposed to remodel. It doesn’t eliminate the risk entirely, but it meaningfully lowers it. For women without clear risk factors, routine aspirin is not recommended. Regular prenatal visits remain the most reliable way to catch preeclampsia early, since blood pressure monitoring and urine testing can detect the condition before symptoms appear. Early detection allows for closer monitoring and, when necessary, timely delivery before the most severe complications develop.