High blood pressure, also called hypertension, occurs when the force of the blood pressing against the walls of the arteries is too high. Generally, normal blood pressure should fall below 140/90 during a blood pressure reading. If either number is significantly over this normal range, the doctor will diagnose hypertension. In pregnancy, some women develop gestational hypertension, which lasts only through the pregnancy. Others start their pregnancy with chronic hypertension. High blood pressure can cause a variety of complications for both mother and baby.
Placental Abruption
In some cases, hypertension can cause the placenta to separate from the uterine wall, leading to excessive bleeding in the mother and a loss of vital oxygen and nutrients for the fetus. If this occurs, it is considered a medical emergency and the baby should be delivered immediately.
Low Birth Weight
High blood pressure in pregnancy can restrict the flow of blood to the placenta because the blood vessels leading to it become constricted, according to the March of Dimes. This can result in a fetus who does not gain weight or get enough of the nutrients he needs, a condition called restricted fetal growth. Ultimately, a severe restriction of the placental blood can lead to a low birth-weight baby, under 5 1/2 lbs., if the blood flow to the fetus is not restored.
Preeclampsia
Preeclampsia is a dangerous condition in which the mother experiences extremely high blood pressure and also develops protein in her urine. If left untreated, preeclampsia can rapidly lead to eclampsia, which is characterized by seizures, coma or even death of the mother. High blood pressure linked to preeclampsia occurs after the 20th week of gestation.
Preterm Labor
Often, a woman who develops severe hypertension that endangers her life or the life of her baby will be recommended for early delivery, before 37 weeks gestation, by her doctor. While premature labor carries its own risks, a woman's doctor may decide that the risks inherent in preeclampsia or fetal growth restriction are higher than the risk of preterm labor and early delivery. Often, the doctor will attempt to wait until between 34 to 37 weeks to deliver the baby, since late preterm delivery during this period gives the baby a high chance of survival without future medical complications.
Heart Disease
Although the evidence is thus far inconclusive, there may be a link between high blood pressure during pregnancy and the future incidence of heart disease, according to the Mayo Clinic. There may even be an increased risk of cardiovascular disease in women whose blood pressure returns to normal after delivery.
