Hypertension (high blood pressure) is defined as blood pressure higher than 140/90 mmHg. Essential hypertension (high blood pressure with no underlying anatomic cause) accounts for 90% of hypertension in non-pregnant patients. Hypertensive disorders of pregnancy are among the leading causes of death among expectant mothers. Severe hypertension increases the mother's risk of heart attack, heart failure, stroke, and kidney failure. The baby is also at increased risk from complications, such as poor placental transfer of oxygen, growth restriction, premature birth, and placental abruption (separation of the placenta from the uterus). There are two different types of hypertension in pregnancy. One type is hypertension that was present before pregnancy and may be aggravated by pregnancy. Pregnancy-induced hypertension, on the other hand, begins during pregnancy, is caused by the pregnancy, and disappears after the delivery of the baby. Either type of hypertension may require the mother to take medications that both control blood pressure and are safe to take during pregnancy. Severe pregnancy-induced hypertension may develop into a condition called preeclampsia, which requires special medicine to be administered to the mother during labor and delivery.