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High-Risk Pregnancy - Chronic Hypertension

What is chronic hypertension?

Blood pressure is the force of the blood pushing against the artery walls. Each time the heart beats, it is pumping blood into these arteries - resulting in the highest blood pressure when the heart contracts and is pumping the blood. High blood pressure, or hypertension, directly increases the risk of coronary heart disease (heart attack) and stroke (brain attack). Hypertension is defined in an adult as a blood pressure:

  • greater than or equal to 140 mm Hg systolic pressure (Pressure is at its greatest when the heart contracts and is pumping the blood - called systolic pressure.)
  • greater than or equal to 90 mm Hg diastolic pressure (When the heart is at rest, in-between beats, blood pressure falls - called diastolic pressure.)

When a woman has pre-existing hypertension or develops hypertension before the 20th week of pregnancy, this is called chronic hypertension. Less than 3 percent of women have this condition.

Other forms of hypertension in pregnancy include gestational hypertension, also known as toxemia or preeclampsia. Some women with chronic hypertension also develop gestational hypertension, resulting in a potentially serious condition.

How does pregnancy affect chronic hypertension?

Most risks are not increased for most women with mild chronic hypertension if there are no other complications. However, if hypertension is severe, if there are other conditions such as diabetes, or if gestational hypertension develops along with chronic hypertension, risks are much greater for mother and baby.

Risks of severe chronic hypertension in pregnancy may include, but are not limited to, the following:

  • blood pressure increasing
  • congestive heart failure
  • bleeding in the brain
  • kidney failure
  • placental abruption (early detachment of the placenta from the uterus)
  • blood clotting disorder

Risks to the fetus and newborn depend on the severity of the disease and may include, but are not limited to, the following:

  • intrauterine growth restriction (IUGR) - decreased fetal growth due to poor placental blood flow.
  • preterm birth (before 37 weeks of pregnancy)
  • stillbirth

Management of chronic hypertension during pregnancy:

Prenatal care and careful monitoring of blood pressure and other factors are important. Women with high blood pressure often need to continue taking their antihypertensive medication. Your physician may switch you to a safer antihypertensive medication during pregnancy.

Laboratory tests may be performed on a regular basis to check the levels of various blood and urine substances related to hypertension. Other tests to monitor heart and kidney function may also be performed. Fetal testing may begin in the second trimester and may include:

  • ultrasound (to measure fetal growth)
  • nonstress test - measures fetal heart rate in response to fetal movement.
  • biophysical profile - a test that combines an ultrasound with the nonstress test.
  • Doppler flow studies - a type of ultrasound which use sound waves to measure blood flow.

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