High blood pressure, a condition in which blood moves through the body's arteries at too great a force, can be dangerous for pregnant women and their fetuses alike. High blood pressure affects about six to eight percent of all U.S. pregnancies, states the National Heart, Lung, and Blood Institute. While doctors don't know the exact causes of high blood pressure in expectant mothers, several factors may contribute to it.
Pre-Existing Blood Pressure Problems
Sometimes women have high blood pressure before becoming pregnant, but don't realize it until they start getting prenatal care. Whatever blood pressure problems a women had before pregnancy will carry over into pregnancy, FamilyDoctor.org explains, putting the unborn baby at risk, as well as the expectant mother. Some women develop high blood pressure after they become pregnant, but those who had high blood pressure before pregnancy are at greater risk of pregnancy complications than those who developed the condition after they conceived, says the National Heart, Lung, and Blood Institute. A particularly dangerous complication that women with pre-existing high blood pressure are at risk for developing is preeclampsia, a condition marked by very high blood pressure and protein in the urine, which tends to show up after the 20th week of pregnancy, and can damage the placenta and the mother's kidneys, liver, and brain, according to the National Heart, Lung, and Blood Institute.
Underlying Diseases
Certain diseases can elevate a pregnant woman's blood pressure and require medical treatment to address the root of the problem. The National Heart, Lung, and Blood Institute states that kidney disease, lupus, diabetes, scleroderma, and rheumatoid arthritis each commonly cause high blood pressure in pregnant women. Women who develop preeclampsia during pregnancy may find their blood pressure return to normal for a while after delivering their babies, notes the Mayo Clinic, but later in life, they're more prone than others to developing cardiovascular disease.
Weight
Obese pregnant women are more likely than expectant mothers of normal weight to develop high blood pressure during pregnancy, says the National Heart, Lung, and Blood Institute. The Mayo Clinic recommends that women who are overweight meet with a doctor to discuss how best to lose excess pounds before they try to conceive. The Mayo Clinic also cautions pregnant women to avoid gaining too much weight during pregnancy, since extra weight will place stress on their hearts, which could raise blood pressure.
Age
Pregnant women who are under age 20 or over age 40 are at greater risk than expectant mothers between 20 and 40 years old of developing high blood pressure and preeclampsia, according to the National Heart, Lung, and Blood Institute.
