Chronic Hypertension in Pregnancy
Donald Aulds, M.D.
The definition of chronic hypertension in pregnancy has been established by the National High Blood Pressure Education Working Group as hypertension present before the 20th week of pregnancy or hypertension occurring prior to the onset of pregnancy. The blood pressure is recommended to be taken in an upright position after a 10 minute rest period. It is also recommended that the patient should not have consumed caffeine or used tobacco for thirty minutes prior to the blood pressure reading. The following criteria are used as guidelines for diagnosing chronic hypertension in pregnancy:
- Mild: Systolic blood pressure > 140 mm Hg and diastolic blood pressure > 90 mm Hg
- Severe: Systolic blood pressure > 180 mm Hg and diastolic blood pressure > 110 mmHg
- Use of antihypertensive medications before pregnancy
- Onset of hypertension before the 20th week of pregnancy
For a true diagnosis of hypertension, the blood pressure should be elevated on more than one occasion.
Chronic hypertension is usually different from the more common pregnancy induced hypertension (PIH) which usually occurs after the 20th week of pregnancy and usually resolves after delivery during the postpartum period. Preeclampsia is a condition of hypertension which is often associated with protein in the urine, headaches, spots before the eyes, upper abdominal pain, and abnormal blood studies. Preeclampsia can occur in pregnant women who have chronic hypertension.
What are the effects of chronic hypertension on pregnancy?
Chronic hypertension has been often associated with risks of preterm labor, premature births, decreased fetal growth, premature separation of the placenta, and higher risk of needing a Cesarean section. In a recent study, women with chronic hypertension whose blood pressure was not controlled had as high as 60-70% risk of having a preterm delivery. The study also showed that half of the patients had superimposed preeclampsia. Another study showed that more than two thirds of babies born to mothers with uncontrolled hypertension were small for gestational age at birth. Pregnancy has a risk of worsening the hypertension, decreasing the heart’s ability to compensate for the extra work load and cause deterioration of the function of the kidneys.
Who should be treated for hypertension in pregnancy?
Women who are already on antihypertensive medication should not be advised to stop their medications but the medications may need to be changed to a preparation that is commonly used in pregnancy. Studies have reported that use of medications in women with mild chronic hypertension has not decrease that incidence of complications such as retarded infant growth, preeclampsia, or premature separation of the placenta. The National High Blood Pressure Working Group has suggested that therapy could be initiated with blood pressures exceeding 150-160 mmHg systolic and 100-110 diastolic. The most commonly used medications during pregnancy for hypertension are methyldopa (Aldomet) and labetalol.
Pregnant women with uncomplicated chronic hypertension of a mild degree generally are able to be delivered at term vaginally if no other complications occur. Women with severe chronic hypertension most often are delivered prematurely for fetal or maternal indications and safety.
If you have chronic hypertension and are considering pregnancy, it is best to consult with your physician prior to conceiving. Discussions need to be undertaken about the pregnancy and management of the pregnancy. If you become pregnant and have chronic hypertension, see an obstetrician during the first trimester of the pregnancy to establish a program of management for the pregnancy.
More about Dr. Aulds
Donald G. Aulds, MD is an Obstetrician and Gynecologist and currently serves as the Medical Director for both the Women's Center and the Best Start Program of North Alabama. He is a Diplomat of the American Board of Obstetrics and Gynecology and Fellow of the American College of Obstetricians and Gynecologists.
Dr. Aulds completed his medical education at Louisiana State University School of Medicine, New Orleans, LA and his Internship and Residency in Obstetrics and Gynecology at Ochsner Medical Foundation, New Orleans, LA.
Dr. Aulds has been an active member of the Huntsville Hospital Medical Staff since 1980.
