Pre-eclampsia is a serious condition that can develop during pregnancy, bringing new-onset high blood pressure and signs of organ damage after the 20th week of gestation. Though many women with this condition go on to deliver healthy babies, understanding the warning signs and getting proper care can be life-saving for both mother and child.

How Common is Pre-eclampsia?

Pre-eclampsia affects between 2% and 8% of all pregnancies worldwide, making it one of the more common complications that can arise during pregnancy. In the United States specifically, it complicates about 5% to 8% of all births and is responsible for roughly 15% of premature deliveries—those that happen before 37 weeks of pregnancy^[3][6].

The global impact of pre-eclampsia is substantial. Each year, this condition contributes to approximately 46,000 maternal deaths and around 500,000 fetal or newborn deaths across the world. In different regions, the burden varies considerably. Pre-eclampsia and its severe form, eclampsia (which involves seizures), account for about 10% of maternal deaths in Asia and Africa, but this percentage rises to 25% in Latin America^[8].

Despite these concerning numbers, the outlook for women with pre-eclampsia in well-resourced countries has improved significantly with proper prenatal care. With appropriate monitoring and timely intervention, most pregnant women who develop pre-eclampsia and their babies survive without serious complications. However, the condition remains a leading cause of illness for both mothers and newborns, even when the best medical care is available^[2].

What Causes Pre-eclampsia?

The exact cause of pre-eclampsia remains unknown, which makes it challenging for doctors to predict exactly who will develop the condition. However, research has provided important clues about what might be happening in the body when pre-eclampsia occurs^[1].

Experts believe that pre-eclampsia begins with problems in the placenta—the organ that connects the baby’s blood supply to the mother’s. During early pregnancy, specifically in the first trimester, the placenta normally anchors itself deeply into the wall of the uterus. In women who later develop pre-eclampsia, this process doesn’t happen as it should. The placenta doesn’t embed itself as deeply as expected, and the blood vessels that develop between the uterine wall and placenta are abnormal^[4].

These early abnormalities in how the placenta forms lead to problems with blood flow. The placenta and developing baby don’t receive an optimal supply of oxygen and nutrients. As pregnancy progresses, these placental problems trigger changes throughout the mother’s body. Arteries—the blood vessels that carry blood from the heart to other parts of the body—begin to tighten and become narrower, which causes blood pressure to rise. These blood vessels can also become “leaky,” allowing protein and fluid to seep through their walls. This leakage causes tissues to swell, a condition called edema^[24].

What specifically causes these placental problems in the first place is still being investigated. Researchers believe it may be influenced by several factors, including the mother’s genes, the father’s genes (passed to the baby and its placenta), the mother’s immune system, and any pre-existing medical conditions the mother may have, such as diabetes or high blood pressure^[14].

Who is at Risk for Pre-eclampsia?

While any pregnant woman can develop pre-eclampsia, certain factors increase the likelihood of developing this condition. Healthcare providers classify these risk factors as either high-risk or moderate-risk categories^[6].

High-risk factors include having a history of high blood pressure, kidney disease, or diabetes before becoming pregnant. Women who are expecting twins, triplets, or more babies are also at higher risk, likely because these pregnancies involve more placental tissue. Autoimmune conditions such as lupus (a condition where the immune system attacks the body’s own tissues) or antiphospholipid syndrome (a disorder that affects blood clotting) also place women in the high-risk category^[3].

Personal and family history also matters significantly. Women who experienced pre-eclampsia in a previous pregnancy are more likely to develop it again. Having a mother, sister, or daughter who had pre-eclampsia also increases risk. Interestingly, if a woman’s male partner had a previous partner who developed pre-eclampsia, this also increases risk, suggesting that the father’s genetic contribution plays a role^[4].

Moderate-risk factors include being pregnant for the first time, being age 40 or older, or being younger than 18 years old. Women who have gone more than 10 years since their last pregnancy, those with obesity (having a body mass index of 35 or higher), and those with a family history of the condition face moderately increased risk. African American and Hispanic women also have higher rates of pre-eclampsia compared to other groups. Having pregnancies through in vitro fertilization (IVF), especially after frozen embryo transfer, also increases risk^[4][5].

Women who have two or more of these risk factors together face even higher chances of developing pre-eclampsia. For those identified as high-risk, doctors may recommend taking a low dose of aspirin (between 75 and 150 mg daily) starting from the 12th week of pregnancy until delivery to help reduce the risk of developing pre-eclampsia^[4][6].

What Are the Symptoms of Pre-eclampsia?

Many women with pre-eclampsia don’t notice any symptoms at all, which is why regular prenatal checkups are so important. The condition is often first detected when a healthcare provider measures blood pressure and tests urine during a routine appointment^[1].

The defining features of pre-eclampsia are high blood pressure (readings of 140/90 mm Hg or higher on two occasions at least four hours apart) and evidence of organ damage, most commonly indicated by protein in the urine. However, pre-eclampsia can also be diagnosed when high blood pressure occurs along with other signs of organ problems, even without protein in the urine^[2].

When symptoms do occur, they can include severe headaches that don’t go away even after taking pain medication. Vision changes are also common—these might include blurred vision, seeing flashing lights or spots, or increased sensitivity to light. Some women experience pain in the upper right side of the abdomen, just below the ribs. This pain can sometimes be confused with heartburn or gallbladder problems^[1][4].

Other symptoms include sudden swelling of the face, hands, or feet. While some swelling is normal during pregnancy, especially in the ankles and feet, sudden or severe swelling—particularly in the face and hands—should be reported to a healthcare provider immediately. Shortness of breath, nausea and vomiting (especially after the first trimester), and sudden weight gain are also warning signs^[4].

Severe pre-eclampsia involves even more serious symptoms. Very high blood pressure (160/110 mm Hg or higher) is considered a hypertensive emergency. Signs of severe disease also include decreased kidney or liver function (detected through blood tests), low blood platelet levels (which affects blood clotting), fluid in the lungs making it difficult to breathe, and producing very little or no urine^[3].

It’s important to note that pre-eclampsia can also develop after delivery, a condition called postpartum pre-eclampsia. This typically occurs within 48 hours after giving birth, though it can rarely happen up to six weeks postpartum. Women should remain alert to symptoms even after their baby is born^[1][5].

How Can Pre-eclampsia Be Prevented?

While there is no guaranteed way to prevent pre-eclampsia, certain measures can significantly reduce the risk for women who are most likely to develop the condition. The most effective preventive measure currently available is low-dose aspirin^[6].

For women identified as being at high risk for pre-eclampsia, healthcare providers may recommend taking a daily dose of low-dose aspirin (typically between 75 and 150 mg). This should ideally be started before the 16th week of pregnancy, though it can be initiated any time between 12 and 28 weeks of gestation. The aspirin is continued daily until the baby is born. It’s crucial that women take the aspirin exactly as their provider recommends—not more and not more often than prescribed. This simple intervention has been shown to reduce the risk of developing pre-eclampsia in high-risk women^[6].

Beyond aspirin, attending all scheduled prenatal appointments is essential for early detection. During these visits, healthcare providers check blood pressure and test urine for protein—the two key indicators that can catch pre-eclampsia in its early stages before symptoms develop. Early detection allows for closer monitoring and timely intervention, which can prevent the condition from progressing to more severe forms^[4].

Managing pre-existing health conditions before and during pregnancy is also important. Women with chronic high blood pressure, diabetes, or kidney disease should work closely with their healthcare team to control these conditions, as they increase the risk of developing pre-eclampsia. Maintaining a healthy weight before pregnancy may also help, as obesity is a known risk factor^[5].

Women who have had pre-eclampsia in a previous pregnancy should inform their healthcare provider at the start of any subsequent pregnancy. This information allows for earlier monitoring and preventive measures to be put in place^[4].

How Pre-eclampsia Affects the Body

Pre-eclampsia causes widespread changes throughout the body, affecting multiple organ systems. Understanding these changes helps explain both the symptoms women experience and the potential complications that can arise^[1].

The cardiovascular system is significantly affected. Blood vessels throughout the body tighten and narrow, which increases resistance to blood flow and causes blood pressure to rise. The heart must work harder to pump blood through these constricted vessels, putting stress on this vital organ. The blood vessels also become more permeable, meaning their walls allow fluid and protein to leak out into surrounding tissues. This is what causes the swelling that many women with pre-eclampsia experience^[3].

The kidneys are particularly vulnerable in pre-eclampsia. Normally, the kidneys filter waste products from the blood while keeping important substances like proteins inside the blood vessels. In pre-eclampsia, damage to the small blood vessels in the kidneys allows protein to leak into the urine, a condition called proteinuria. In severe cases, kidney function can decline significantly, and the kidneys may produce very little urine. Blood tests can reveal elevated levels of certain waste products that the kidneys should be filtering out^[5].

The liver can also be affected. Changes in blood flow and blood vessel damage can impair liver function, which shows up as elevated liver enzymes in blood tests. Some women experience pain in the upper right side of the abdomen where the liver is located. In severe cases, complications can affect the liver’s ability to perform its many essential functions^[1].

Pre-eclampsia affects the blood’s ability to clot properly. The condition can cause platelet levels to drop—platelets are tiny blood cells that help form clots to stop bleeding. When platelet counts become too low (a condition called thrombocytopenia), there is an increased risk of excessive bleeding^[1].

The nervous system may be impacted as well. The headaches that some women experience likely result from changes in blood flow to the brain and increased pressure within the skull. Vision problems occur when blood vessels in the eyes and the parts of the brain that process vision are affected. In the most severe cases, these changes can lead to seizures, a complication known as eclampsia, or even stroke^[3].

Perhaps most concerning is how pre-eclampsia affects blood flow to the placenta and baby. The abnormal development of blood vessels in the placenta means the baby may not receive adequate oxygen and nutrients. This can result in slower fetal growth, a condition called fetal growth restriction. Decreased levels of amniotic fluid surrounding the baby can also occur. In severe cases, the placenta can detach from the uterine wall prematurely, a dangerous complication called placental abruption^[3].

In some cases, fluid can accumulate in the lungs, a condition called pulmonary edema. This makes breathing difficult and is a sign of severe disease requiring immediate treatment^[3].