Understanding Preeclampsia and Eclampsia -- the Basics

Medically Reviewed by Traci C. Johnson, MD on March 22, 2023
Written by WebMD Editorial Contributors
2 min read

Preeclampsia and eclampsia are diseases of pregnancy that involve the development or worsening of high blood pressure during the second half of pregnancy. Preeclampsia, formerly called "toxemia of pregnancy," may develop into the more severe condition called eclampsia. Eclampsia includes symptoms of preeclampsia, along with seizures.

These conditions, when they develop, occur after 20 weeks of pregnancy. They also may develop shortly after delivery. 

High blood pressure is dangerous during pregnancy because it may interfere with the placenta's ability to deliver oxygen and nutrition to your fetus. Your baby may be born weighing less than normal, may have other health problems, and may need to be delivered early.

If your blood pressure continues to climb higher, your kidneys may have trouble functioning. You may have changes in the makeup of your blood, such as a destruction of red blood cells (causing anemia), as well as disturbed liver function and decreased platelets (the blood cells involved in clotting). Too few platelets can increase your risk of bleeding uncontrollably during delivery, or even spontaneously. In addition, the high blood pressure may cause the placenta to begin to separate from the wall of the uterus, called a placental abruption. This can cause severe bleeding and even death of the fetus and possibly the mother.

If you begin to have seizures with preeclampsia, you're considered to have eclampsia. This is a life-threatening situation for both you and your baby. During a seizure, you and your baby are at risk of being deprived of oxygen. 

Preeclampsia affects 3% to 7% of all pregnancies in the U.S. Any pregnant woman can get preeclampsia, but you're at increased risk of developing preeclampsia if:

  • This is your first pregnancy
  • Your mother or sister had preeclampsia or eclampsia during pregnancy
  • You're carrying multiples (twins or more)
  • You're African-American
  • You're under age 20 or over age 35 at the time of pregnancy
  • You already have high blood pressure, kidney disease, or diabetes
  • You have a pre-pregnancy body mass index (BMI) greater than 30
  • You had preeclampsia in a previous pregnancy

The cause of preeclampsia is still unclear. Most theories focus on abnormal placental development, blood vessel disruption, immune system, or genetic factors