Preeclampsia does not technically cause miscarriage, but the distinction is more about timing than biology. Miscarriage is defined as pregnancy loss before 20 weeks of gestation, while preeclampsia is diagnosed after 20 weeks. These two conditions occupy different windows of pregnancy by definition. However, the underlying placental problems that lead to preeclampsia can and do cause pregnancy loss, and preeclampsia itself is a significant cause of stillbirth and fetal death later in pregnancy.
Why Timing Matters for This Question
In the United States, miscarriage refers to losing a pregnancy before the 20th week. Stillbirth refers to losing a pregnancy after 20 weeks but before birth. Preeclampsia, characterized by high blood pressure plus signs of organ damage, is diagnosed after 20 weeks of gestation. So by the time preeclampsia appears, any pregnancy loss it causes would be classified as a stillbirth or fetal death rather than a miscarriage.
Cases of preeclampsia appearing before 20 weeks are extraordinarily rare. A review of the medical literature identified only four published cases of true preeclampsia before 20 weeks that weren’t linked to an underlying condition like kidney disease or a molar pregnancy. When high blood pressure and protein in the urine show up that early, it usually points to pre-existing kidney disease rather than preeclampsia. Distinguishing between the two matters because the treatments are different.
How Preeclampsia Causes Pregnancy Loss After 20 Weeks
Preeclampsia can absolutely cause fetal death in the second half of pregnancy, and the earlier it develops, the more dangerous it is. In a study of women with severe preeclampsia before 26 weeks, neonatal survival was only 19%. For those admitted before 24 weeks, survival dropped to just 6.6%. In some cases, the fetus dies in utero before delivery can even be attempted. In others, the pregnancy must be ended early to protect the mother’s life, and the baby is too premature to survive.
The core problem is placental insufficiency. Early in pregnancy, the placenta needs to remodel the blood vessels in the uterine wall, converting them from narrow, high-resistance vessels into wide, low-resistance ones that allow blood to flow freely. When this process fails, the placenta doesn’t get enough blood. That starves the fetus of oxygen and nutrients and can trigger preeclampsia in the mother. This same process contributes to fetal growth restriction, dangerously low amniotic fluid levels, and stillbirth.
Conditions That Cause Both Preeclampsia and Miscarriage
While preeclampsia itself sits on the wrong side of the 20-week line to cause miscarriage, several underlying conditions raise the risk of both. If you’ve experienced pregnancy loss and are worried about preeclampsia, or vice versa, these shared root causes are worth understanding.
Antiphospholipid syndrome (APS) is one of the most important links. APS is an autoimmune condition where the body produces antibodies that promote abnormal blood clotting. It causes recurrent miscarriages, fetal death after 10 weeks, restricted fetal growth, and severe preeclampsia. The connection between APS and preeclampsia was first described in the early 1980s, and multiple studies since have confirmed that women with APS face a significantly higher risk of severe preeclampsia. Women who develop severe preeclampsia are now often screened for APS so that future pregnancies can be managed more safely.
Other conditions that increase the risk of both early pregnancy loss and preeclampsia include chronic high blood pressure, diabetes, lupus, and kidney disease. These conditions impair blood flow to the placenta from the start, setting the stage for complications throughout pregnancy rather than at one specific point.
Warning Signs to Recognize
Preeclampsia sometimes develops without obvious symptoms, which is why blood pressure checks are a routine part of prenatal visits. When symptoms do appear, the most common ones include severe headaches, changes in vision (blurriness, light sensitivity, or temporary vision loss), pain in the upper right abdomen below the ribs, nausea or vomiting that starts in the second half of pregnancy, shortness of breath, and sudden swelling of the face and hands. Sudden, unexplained weight gain can also be a signal.
Severe headaches, visual disturbances, intense abdominal pain, or difficulty breathing warrant immediate emergency care. Preeclampsia can escalate quickly, and early detection is one of the most effective ways to protect both mother and baby.
Reducing Risk in Current and Future Pregnancies
For women at high risk of preeclampsia, low-dose aspirin (81 mg per day) is recommended as a preventive measure. The U.S. Preventive Services Task Force and the American College of Obstetricians and Gynecologists both support starting it after 12 weeks of gestation, ideally before 16 weeks, and continuing daily until delivery. This small daily dose helps improve blood flow through the placenta and has been shown to reduce the incidence of preeclampsia in high-risk pregnancies.
If you’ve had preeclampsia before, the chance of it recurring in a future pregnancy ranges from about 13% to 55% depending on the study, with roughly one in four women experiencing it again. The risk is higher for women who were in their first pregnancy when preeclampsia developed: about 34% recurrence, compared to roughly 12% for women who had already had previous pregnancies. Having preeclampsia in two consecutive pregnancies pushes the recurrence risk for a third pregnancy to about 32%.
The reassuring flip side of these numbers is that a large majority of women, somewhere between 63% and 83%, who had preeclampsia in one pregnancy go on to have normal blood pressure in subsequent pregnancies. Knowing your history and risk factors allows your care team to monitor you more closely and intervene early if needed.