What are the types of high blood pressure during pregnancy?

Sometimes high blood pressure begins before pregnancy. In other cases, the condition develops during pregnancy.

• Chronic hypertension. In chronic hypertension, high blood pressure develops either before pregnancy or during the first 20 weeks of pregnancy. Because high blood pressure usually doesn't have symptoms, it might be hard to know exactly when it began.
• Chronic hypertension with superimposed preeclampsia. This condition occurs when chronic hypertension leads to worsening high blood pressure during pregnancy. People with this condition may develop protein in the urine or other complications.
• Gestational hypertension. People with gestational hypertension have high blood pressure that develops after 20 weeks of pregnancy. There's no excess protein in the urine and there are no other signs of organ damage. But in some cases, gestational hypertension can eventually lead to preeclampsia.
• Preeclampsia. Preeclampsia occurs when hypertension develops after 20 weeks of pregnancy. Preeclampsia is associated with signs of damage to other organ systems, including the kidneys, liver, blood or brain.

Untreated preeclampsia can lead to serious — even fatal — complications for mother and baby. Complications may include eclampsia, in which seizures develop.

Previously, preeclampsia was diagnosed only when both high blood pressure and protein in the urine were present. Experts now know that it's possible to have preeclampsia without having protein in the urine.