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High blood pressure occurs in 20 percent of pregnancies

April 30, 2014

Written by Dr. Torre Halscott, Senior Resident, OB/GYN

Elevated blood pressure is one of the more common illnesses in pregnancy, occurring in some way in up to 20 percent, or 1 out of every 5, pregnancies. This condition can lead to problems for the mother as well as the fetus while still in the uterus, and even for the baby after delivery. While most of these unfortunate outcomes are rare, they can potentially be very serious, and occasionally even life-threatening.

Some of the maternal problems that high blood pressure can lead to in pregnancy are:

  • placental abruption (when the placenta separates from the uterus prematurely)
  • HELLP syndrome (a condition with abnormal liver and platelet function)
  • pulmonary edema (excess fluid in the lungs)
  • eclampsia (seizures during pregnancy)
  • kidney or liver failure, stroke, and even death

Problems for the fetus and baby include:

  • preterm birth (either spontaneously or to protect the mother or baby)
  • growth restriction (the fetus not gaining weight appropriately)
  • low birth weight
  • low amniotic fluid (the liquid around the baby inside the womb)
  • brain injury and in rare cases, death
While these conditions sound scary, working together with your doctor to prevent, diagnose, manage, and treat potential problems, the best outcome for you and your baby can hopefully be achieved.

To have elevated blood pressure during pregnancy, a patient has to have a systolic reading (the larger number) of at least 140, or a diastolic pressure (the smaller number) of at least 90, two or more times, each of which is at least six hours apart from each other.

The four main types of high blood pressure in pregnancy are:

Chronic hypertension (often abbreviated as (CHTN)

High blood pressure that was either diagnosed before pregnancy began, or begins earlier than the 20th week (approximately 5th month) of gestation.

Gestational hypertension (GHTN)

High blood pressure that starts after the 20th week of pregnancy, resolves within the first 12 weeks after delivery, and DOES NOT have increased protein in the urine.

Preeclampsia (PreE)

Elevated blood pressure that starts after the 20th week, resolves by 12 weeks postpartum, and is accompanied by abnormal protein in the urine.

  • Abnormal urine protein is often assessed by testing with a dipstick that is placed into a urine sample, though a more complete evaluation is by measuring all of the protein that is passed in a 24 hour collection (greater than 300 mg in 24 hours is abnormal).
  • Preeclampsia is traditionally thought of as the condition that most commonly precedes eclampsia (seizures due to elevated blood pressure in pregnancy).
  • Preeclampsia is further split into two types:
    • Mild preeclampsia – when the blood pressure stays below 160 systolic (the larger number), or 110 diastolic (the smaller number), and there are no symptoms of severe disease.
    • Severe preeclampsia– when blood pressure exceeds 160 systolic or 110 diastolic, and/or certain symptoms are present (listed below).
      • Unrelenting headaches, persistent visual changes, difficulty breathing due to excess fluid in the lungs, severe upper abdominal pain, liver dysfunction, significantly low platelets (part of the blood that helps it clot), very decreased urine output, more than 5000 milligrams of protein in a 24 hour sample, or a fetus that is extremely small or has too little amniotic fluid around it.
  • Preeclampsia is believed to be due to problems with how the placenta implants into the wall of the uterus, and how the body then reacts to this issue.
Chronic hypertension with superimposed preeclampsia (CHTN-siPreE)

When a patient that has CHTN (by the definition above), also develops preeclampsia (diagnosed by the same urinary protein measurements as for preeclampsia on its own).

  • Of all the conditions with elevated blood pressure in pregnancy, this has the highest risk of serious adverse outcomes, though they are still uncommon overall.
If you have one of these conditions during pregnancy, your doctor will almost always make changes to your care to follow them more closely. This includes more ultrasounds, usually one a month, to make sure that the growth of your baby is stable. You should also have non-stress tests (NST) two times per week, or a biophysical profile (BPP) once a week. These are specialized ways of monitoring a baby in the womb to potentially detect when issues are arising. In addition to further testing, patients often require medications to control their blood pressure. There are many safe and effective blood pressure medications for pregnant women; some examples are labetalol, methyldopa, nifedipine, and hydralazine among others. Lastly, high blood pressure in pregnancy almost always requires delivery before a patient’s due date. For those with CHTN, this is commonly at 38 to 39 weeks (1 to 2 weeks prior to the due date); with preeclampsia delivery is most often at 37 weeks for mild disease and by 34 weeks for severe preeclampsia and chronic hypertension with superimposed preeclampsia. In rare cases where severe symptoms or blood pressure cannot be controlled, delivery can be performed sooner, as this eliminates the cause of the disease (the interaction between the pregnancy and the mother).

While these potential complications can be worrisome and even dangerous, with your doctor’s efforts along with your own, the chances of having a healthy pregnancy and childbirth are high. By all of us doing our best to diagnose and treat high blood pressure in pregnancy, we can give mothers and babies their best start possible in life together.