Preeclampsia is a pregnancy complication characterized by high blood pressure and signs of damage to another organ system (usually the liver and kidneys). It usually occurs after 20 weeks of pregnancy.

Signs of preeclampsia include high blood pressure, swelling of the face and extremities and a significant increase in protein in the urine. The true cause of preeclampsia is not well understood. However, known risk factors include age of the mother (first pregnancy after the age of 35), twins or other multiples, diabetes, chronic hypertension, kidney disease, rheumatological diseases and preeclampsia in the family history. 

You should immediately consult a doctor if after 20 weeks of pregnancy you have suspicions of preeclampsia. A blood pressure reading above 140/90 mm Hg (measured several times), is considered abnormal during pregnancy. However, if you normally have low blood pressure, then even normal values (for example, 120/80 or 130/90 mm Hg) can lead to complications if left untreated. This includes convulsions or seizures (eclampsia), premature birth, and stroke or venous thromboembolism in the mother.

Some risk factors are not controllable, but one thing that can be done to reduce risk is to control your pregnancy weight gain, as excessive weight gain can lead to increased cholesterol in the blood and hypertension (high blood pressure).