Preeclampsia is high blood pressure that develops or increases during pregnancy. Eclampsia is a complication of severe preeclampsia that involves seizures.

What is going on in the body?

The placenta is the spongy material in the mother's uterus that nourishes the fetus. Some experts believe that a problem with the placenta causes preeclampsia. The mother has spasms of the blood vessels, which increase her blood pressure. The blood flow to the placenta is impaired. If the blood pressure is not controlled, it can damage the placenta and cause the death of the fetus.

Preeclampsia develops in 5% of pregnant women. It usually occurs after the 20th week of pregnancy. It may be mild or severe. The high blood pressure can affect the brain, kidneys, liver, and lungs. If the high blood pressure in the brain causes bleeding into the brain, the woman may have seizures. This complication is called eclampsia.

One in 200 pregnant women who have preeclampsia will go on to have eclampsia. The seizures of eclampsia are marked by general abnormal electrical activity in the brain. Usually the seizures start before the baby is born. However, about 20% to 25% of the time, seizures begin within the first 24 hours after the baby is born. A few women develop seizures later, up to 3 weeks after the birth.

What are the causes and risks of the condition?

Factors that increase a woman's risk of preeclampsia are:

No one knows why some women with preeclampsia develop the seizures associated with eclampsia. Theories about why seizures might occur in pregnancy involve: