Hypertensive Disorders of Pregnancy Overview

Hypertensive disorders of pregnancy are a group of conditions in which blood pressure becomes elevated before, during, or shortly after pregnancy, posing serious risks to both the pregnant woman and her fetus. Major forms include chronic hypertension (present before pregnancy or before 20 weeks gestation); gestational hypertension (developing after 20 weeks gestation); and pre-eclampsia, a more severe disorder characterized by hypertension and signs of damage to organs such as the kidneys or liver.^{1 - 7} These signs often include proteinuria.^{2 , 5 - 7} Pre-eclampsia increases the risk of placental abruption, preterm birth, low birth weight, and other adverse outcomes. It can also progress to eclampsia, which is defined by the onset of maternal seizures. In severe cases, pre-eclampsia and eclampsia can lead to coma; blindness; or hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome, in which damage to the liver and blood cells occurs.^{1 - 3 , 6 - 9}

Several risk factors contribute to the development of hypertensive disorders of pregnancy. The risk is higher among women with pre-existing hypertension, diabetes, kidney disease, obesity, autoimmune diseases (e.g., lupus), or previous pre-eclampsia and in women whose pregnancies were achieved through assisted reproductive technology. It is also higher in women who are under age 20 or over age 40 and in those who are pregnant for the first time or carrying multiple fetuses.^{1 , 3 , 4 , 6 , 9 - 12} Women who are Black, American Indian, or Alaska Native are also at higher risk of developing hypertension during pregnancy.^{1 , 5 , 9 - 11} Family history and certain genetic or immune factors may also play a role. Although the exact causes of pre-eclampsia and eclampsia are not fully understood, researchers are exploring factors that may contribute to the development and progression of these conditions, including placental abnormalities, such as insufficient blood flow; genetic, environmental, and nutritional factors; autoimmune disorders; cardiovascular and inflammatory changes; and hormonal imbalances.³

Hypertensive disorders of pregnancy affect up to about 16% of pregnant women, and they are linked to the physiologic demands placed on the cardiovascular system during gestation.^{2 , 4 , 9 , 13} Importantly, hypertensive disorders of pregnancy are now recognized as early indicators of future cardiovascular risk; women who develop pre-eclampsia or gestational hypertension are more likely to experience chronic hypertension and cardiovascular disease, including heart disease or stroke, later in life.^{3 , 5 , 9 , 10 , 14} In addition, recent research that was partially supported by the National Heart, Lung, and Blood Institute (NHLBI) found that women who had pre-eclampsia or other hypertensive disorders during pregnancy had a 13% to 27% higher risk of all-cause mortality up to 46 years after delivery.^{15 , 16}

Certain therapies can reduce the risk of developing hypertensive disorders of pregnancy, including administering low-dose aspirin (81 mg/day) after 12 weeks gestation to high-risk women,^{6 , 7 , 13} moderate-intensity aerobic exercise,^{17 , 18} and calcium supplementation for pregnant women who have inadequate calcium intakes (e.g., less than 600 mg/day).¹⁹

Diagnosis, treatment, and research efforts for hypertensive disorders of pregnancy focus on early detection, careful monitoring, prevention of complications, and identifying and acting on modifiable risk factors prior to a subsequent pregnancy. Diagnosis is based on repeated blood pressure measurements; clinical symptoms, including swelling in the face and hands, headache, and blurred vision; and evaluation for organ involvement through urine and blood tests.^{3 , 4} Treatment depends on severity and gestational age and may include close surveillance, medications to control blood pressure, and—in severe cases—early delivery.^{2 , 3 , 5 , 9 - 11 , 20} For patients with severe pre-eclampsia, magnesium sulfate is recommended to help prevent the seizures associated with eclampsia.^{3 , 5 , 6}

Ongoing research seeks to identify predictive biomarkers—such as the ratio of soluble fms‑like tyrosine kinase‑1 to placental growth factor—to improve the risk stratification for progression to pre-eclampsia and support the clinical management of women who are affected by hypertensive disorders of pregnancy.^{21 , 22} Other research aims to better understand the biological mechanisms of abnormal placental development, establish optimal blood pressure treatment thresholds, and improve strategies to reduce the long-term risk of cardiovascular disease.^{3 , 5} Additional research is also needed to clarify the association between hypertensive disorders of pregnancy and long-term chronic kidney disease risk in both the mother and infant, as well as other adverse effects on infant health.^{3 , 23}

The nuMoM2b Heart Health Study, which is cofunded by NHLBI and the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), is studying the effects of pregnancy complications on future maternal cardiovascular health. As part of this effort, which has involved more than 6,000 women who have volunteered as study participants, researchers identified links between hypertensive disorders of pregnancy and elevated risks of hypertension, heart disease, and stroke later in life. A deeper understanding of these processes will help guide the development of more effective strategies to predict, prevent, and treat these conditions after pregnancy.

NICHD supports a number of other research initiatives related to pre-eclampsia and eclampsia, including those investigating genetic factors that affect blood pressure during pregnancy, how proteins and other compounds in the blood may signal the onset of pre-eclampsia, and the role of obesity and genetics in the development of pre-eclampsia.