Methyldopa is used to treat high blood pressure. Methyldopa is in a class of medications called antihypertensives. It works by relaxing the blood vessels so that blood can flow more easily through the body. Methyldopa can prevent the complications caused by hypertension (high blood pressure) in pregnancy, and a related condition called pre-eclampsia. These complications include preterm birth, low birth weight in the baby, and illness in both the mother and baby which is sometimes serious.