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High Blood Pressure in Pregnancy
A risk for both mom and baby

High blood pressure, or hypertension, affects about 10 per cent of pregnancies. High blood pressure that begins in pregnancy is called Gestational Hypertension (GHTN). Through the years, different terms have been used for GHTN. Some may remember the term toxemia which is no longer used to describe the severe condition. (See Definitions sidebar for current terms.)

GHTN is more likely to occur in first or twin pregnancies and in women with a family history of the problem. Women who already have high blood pressure or kidney disease are most at risk. There are other medical diseases that also increase the risk. In such cases, pregnancy and medication adjustments should be discussed with a doctor before becoming pregnant.

GHTN can cause serious complications, including liver damage, fluid in the lungs, kidney and heart failure. It may also affect the brain, possibly causing seizures or stroke. In severe cases, the condition can be life threatening for both mother and baby.

What is normal blood pressure in pregnancy?

Normally, blood pressure drops in the second three months of pregnancy and rises again near the end. At each prenatal visit, the doctor will measure blood pressure to check that it is within normal range. The earlier high blood pressure changes occur, the more serious the condition may become.

If blood pressure has risen significantly, or is greater than 140/90 mm Hg, closer follow-up will be arranged. As a first step, blood pressure readings should be taken on several occasions to find out if there really is a problem. For some women, just walking into a medical office increases blood pressure. At other times, the blood pressure is normal. This woman and her pregnancy are not at risk. This condition is called ‘white coat hypertension’. A woman with this issue may learn how to record blood pressure at home. Her doctor can review the results with her later.

Is there any way to tell if I have GHTN?

Signs that suggest GHTN may be present or getting worse include:

• changes in vision like spots before the eyes
  or blurred vision
  
• headache
  
• pain and tenderness at the top of the abdomen
  
• nausea
• generally feeling unwell
  
• sudden weight gain along with widespread or dramatic swelling (not just lower leg swelling, which is common in normal pregnancies).

Tests can check the severity of GHTN. They include blood testing, checking urine for protein, and assessing the baby’s health using ultrasound, heart monitoring and counting of movements.

Can GHTN be treated?

It is best to reduce the risk of developing GHTN by following a healthy lifestyle. In pregnancy, this includes:

• moderate exercise
  
• using vitamin supplements including folic acid.

If GHTN develops, treatment often does not require medication and may or may not require a stay in hospital. Treatment may include:

• making sure that calcium intake is adequate for pregnancy
  
• trying to be as close to ideal body weight as possible before pregnancy
  
• quitting smoking
  
• avoiding alcohol
  
• medical leave from work
  
• high blood pressure medication.

The mother’s health will be monitored by testing her blood and urine regularly. The baby’s health will be monitored by ultrasound once the condition is diagnosed. These measures may be all that is required until delivery. Birth of the baby is the cure for GHTN.

If the mother is admitted to hospital, the baby’s development inside the uterus (womb) will be checked regularly with ultrasound and fetal heart rate monitoring. With GHTN, the flow of blood to the baby through the placenta (the baby’s life support system) can be severely limited. The baby may be very small, born early, or stillborn. Separation of the placenta from the wall of the uterus (placental abruption) is another possibility. For these reasons, labour is often induced (brought on) to deliver the baby early.

The mother is watched for evidence of liver damage, kidney failure and uncontrolled high blood pressure. She may be asked to collect all of her urine for 24 hours for testing. Or, she may pass urine on a test strip several times a day to measure the level of protein. As the clotting of her blood may be affected, it needs testing. Her knee reflexes will likely be tested to check for the development of neurological problems.

Various medications are used to treat GHTN. Some women known to be at risk are advised to take low dose Aspirin™ (80 milligrams), starting early in pregnancy. Eating a diet with enough calcium helps prevent the condition. Most drug treatment involves controlling blood pressure with medication and trying to prevent seizures with medication. Magnesium sulphate is most commonly used for this. It can have serious side effects so mothers using this drug are supervised very closely.

Will GHTN affect my labour and delivery?

Delivery of the baby is the treatment of choice in GHTN. When deciding the best time for birth, the doctor must weigh the risk of a premature baby against the risks to mother and baby if the pregnancy continues.

During labour and delivery, both mother and baby are observed carefully. Pain relief, such as an epidural, may reduce the mother’s stress and keep her blood pressure and condition stable. The baby’s heart rate is monitored closely during the labour since blood flow to baby is often decreased by the condition.

After delivery GHTN may continue, so the mother’s blood pressure is monitored until it returns to normal. If medications are necessary after delivery, their effect on breast feeding must be considered although several medications are safe for use while breast feeding.

It is still not possible to identify all women at risk of GHTN. Very few women develop GHTN that is severe enough to require all the treatments mentioned. However, even with milder GHTN, care must be taken. Complications that could be life threatening to mother and baby could develop. It is very important that women who are pregnant see their doctors regularly for prenatal care, including blood pressure monitoring.