If you are pregnant, high blood pressure can cause problems for you and your unborn baby. You may have had high blood pressure before you got pregnant. Or you may get it once you are pregnant - a condition called gestational hypertension. Either one can cause low birth weight or premature delivery of the baby.
Controlling your blood pressure during pregnancy and getting regular prenatal care are important for the health of you and your baby. Treatments for high blood pressure in pregnancy may include close monitoring of the baby, lifestyle changes, and certain medicines.
Some pregnant women with high blood pressure develop preeclampsia. It's a sudden increase in blood pressure after the 20th week of pregnancy. It can be life-threatening for both you and the unborn baby. There is no proven way to prevent it. Most women who have signs of preeclampsia are closely monitored to lessen or avoid complications. The only way to "cure" preeclampsia is to deliver the baby.
NIH: National Heart, Lung, and Blood Institute