Women are often concerned with their blood pressure during pregnancy. Many question what a normal blood pressure should be, what causes an abnormal blood pressure and how abnormal blood pressure can affect their baby. Keeping track of your blood pressure before and during pregnancy, and making sure to treat it when necessary, can help prevent any potential problems. It is important to have your blood pressure checked by your doctor each time you go for a prenatal visit.
Blood pressure during pregnancy
What is blood pressure? Blood Pressure is the pressure that is exerted upon the walls of the blood vessels by the blood circulating through the body at any given time. In simpler terms, it is the pressure of your blood flowing through your body. Blood pressure can be too high, known as hypertension, or too low, known as hypotension. While both of these conditions are concerning for a woman who is not pregnant, they are a critical matter for a woman who is pregnant.
How is blood pressure read?
Systolic: The top number, known as systolic, is the higher of the two numbers and represents the pressure measured in the arteries when the heart beats (contracts).
Diastolic: The bottom number, known as diastolic, is the lower of the two numbers and represents the pressure measured between heartbeats.
Current guidelines identify normal blood pressure as equal to or lower than 120/80 mm
Low blood pressure during pregnancy
Low blood pressure during pregnancy is not generally a common concern because it is often expected and does not typically cause many problems. During the first 24 weeks of pregnancy, blood pressure is known to drop to between 5 and 10 mm Hg systolic and between 10 and 15 mm Hg diastolic. This is considered normal and it will rise again after birth. The only concern with low blood pressure is if it drops suddenly and significantly. Usually the effects are experienced by dizziness and fainting and immediate care is necessary.
High blood pressure during pregnancy
There are various classifications of hypertension during pregnancy. The classifications are characterized by the severity of the hypertension and the stage of pregnancy. In general, there are four classifications:
- Chronic Hypertension: Chronic Hypertension refers to hypertension which develops before the 20th week of pregnancy or is already present before pregnancy. The criterion for chronic hypertension is a systolic number between 140 and 180 mm Hg or a diastolic number between 90 and 100 mm Hg.
- Gestational Hypertension: Gestational Hypertension is hypertension which develops after 20 weeks of gestation, but returns to normal postpartum.
- Preeclampsia: Preeclampsia is the development of high blood pressure after 20 weeks of gestation and the presence of protein in the mother’s urine. The criterion for preeclampsia is a systolic number greater than 140 mm Hg or a diastolic number greater than 90 mm Hg. Severe preeclampsia occurs when the systolic number is greater 160 mm Hg or the diastolic number is greater than 110 mm Hg on two different occasions at least 6 hours apart while the mother is on bed rest. Click here for more information on preeclampsia.
- Eclampsia: Eclampsia describes a condition where the mother experiences convulsions in addition to having preeclampsia. These convulsions cannot be explained by a neurological disorder. Eclampsia occurs in 0.5% to 4% of mothers with preeclampsia.
The concern with high blood pressure during pregnancy is the risk it poses to both the mother and the baby due to the following conditions:
- Premature delivery
- Decreased blood flow to the placenta
- Placental abruption
- Cardiovascular disease later in life
Treating abnormal blood pressure during pregnancy
The main goal of managing blood pressure during pregnancy is balancing the health of the mother along with the fetus to ensure safety for both. The mother and the baby should be carefully monitored the entire duration of the pregnancy. Should it be necessary, your doctor will be able to prescribe the proper medication to help treat abnormal blood pressure. It is important to take the medication as prescribed and let your doctor know of any side effects.
Beckmann, C., Ling, F. W., Barzanksy, B. M., Herbert, W., Laube, D. W., & Smith, R. P. (2010). Obstetrics and Gynecology (6th ed.). Baltimore, MD: Lippincott Williams & Wilkins.
Scott, J. R., Gibbs, R. S., Karlan, B. Y., & Haney, A. F. (2003). Danforth’s Obstetrics and Gynecology (9th ed.). Philadelphia, PA: Lippincott Williams & WIlkins.
www.heart.org (American Heart Association)