High blood pressure, or hypertension, is an increase in blood pressure. You may not experience any symptoms, but some women experience headaches, visual disturbances, water retention, and/or vomiting.
Although high blood pressure can occur at any time during your pregnancy, it is more common near your due date. Women who are having their first baby, who are over 35, or who are having more than one baby are more likely to have high blood pressure.
It's not entirely clear why some women get high blood pressure in pregnancy. Possible causes include:
Preeclampsia occurs in a small percentage of pregnancies. Risk factors include:
In some women, cells from the placenta produce chemicals called vasocontrictors, which constrict blood vessels. This may cause the blood pressure to rise and the kidneys to retain sodium, leading to water retention.
Your blood pressure should return to normal after your baby is born.
A rise in your blood pressure could be a warning of preeclamptic toxemia (PET or preeclampsia). Preeclampsia slows your baby's growth rate and reduces the oxygen available to your baby by reducing the amount of blood flowing to your uterus. This causes low birthweight.
In rare cases, high blood pressure may be a sign of a life-threatening form called eclampsia, but this is usually not the case in countries with good health care.