Blood pressure is a measure of how hard the blood pushes against the walls of the arteries. Blood pressure readings consist of an upper number and a lower number (such as 120 over 80, or 120/80). High blood pressure is a top number of 130 or higher or a bottom number of 80 or higher. Blood pressure is closely watched during pregnancy. High blood pressure can limit the baby’s growth or cause other serious problems.

Some women have high blood pressure before they get pregnant (chronic high blood pressure). Others may develop very high blood pressure that starts in the second or third trimester (gestational hypertension). Sometimes high blood pressure is a first sign of preeclampsia. This condition is dangerous for both mother and baby.