Hypertension During Pregnancy

Hypertension, or high blood pressure, is one of the most common medical conditions detected in pregnancy. For this reason, a woman’s blood pressure is checked regularly during routine antenatal visits.

If blood pressure readings are consistently higher than normal, treatment to lower the blood pressure may become important. Hypertension during pregnancy can cause serious complications for the mother and baby.

Blood pressure is the pressure of the blood against the blood vessel walls as it flows through them. Blood pressure readings in arteries are recorded as two numbers.

The higher reading (systolic blood pressure) measures the pressure against the vessel walls when the heart contracts. Systolic blood pressure is normally about 120mmHg (millimetres of mercury).

The lower reading (diastolic blood pressure) is a measure of the pressure when the heart relaxes between beats. Diastolic blood pressure is normally about 80mmHg.

A normal blood pressure reading is therefore called ‘120 over 80’ and written as 120/80. Hypertension occurs when the blood pressure is consistently 140/90 or higher. Severe hypertension is 170/110 or higher.


Types Of Hypertension During Pregnancy

  • Gestational hypertension: If a woman’s blood pressure is normal before and during the first few months of pregnancy, but rises to more than 140/90mmHg after about 20 weeks of pregnancy with no other signs or symptoms, her condition is known as gestational hypertension.
  • Chronic hypertension: High blood pressure that is present before and during the pregnancy is known as chronic hypertension.
  • Pre-eclampsia: Pre-eclampsia is a potentially serious condition that occurs when the mother’s blood pressure is elevated and other signs and symptoms are present, such as an abnormal level of protein in the urine and abnormal results of blood tests.
  • Pre-eclampsia superimposed on chronic hypertension: This carries a higher risk for mother and baby than chronic hypertension alone, and requires regular monitoring to detect its occurrence.
    Not all women who have hypertension in pregnancy will develop pre-eclampsia. Similarly, not all women who develop pre-eclampsia have previously been diagnosed with gestational or chronic hypertension.

Treatment Of Hypertension During Pregnancy

Women with gestational hypertension and chronic hypertension in pregnancy may be treated with medication to lower blood pressure. Although these conditions are not as serious as pre-eclampsia, it is generally safer for the mother and baby if the mother’s blood pressure stays below 140/90mmHg.

Treatment of Pre-Eclampsia

If the blood pressure is found to be very high (more than 170/110), medication may first be given through a vein or as an intramuscular injection, rather than by mouth. This enables it to work more quickly. Intravenous fluids may be given at the same time, while the woman and baby are monitored closely. Following successful reduction in blood pressure, treatment can often be continued with tablets.
The only way to cure pre-eclampsia regardless of when it occurs is the pregnancy, is to deliver the infant and the placenta. If the pregnancy is less than 36 weeks, the decision to deliver the baby early will be based upon the severity of the pre-eclampsia and the risk of prematurity.

Eclampsia

Eclampsia is a serious condition that causes maternal convulsions and may lead to stroke, kidney failure or liver failure. Eclampsia is a medical emergency that may occur if pre-eclampsia is left untreated or does not respond to vigorous treatment.

Treatment Of Eclampsia

If seizures occur in the mother, she is usually treated immediately with an anti-convulsant medication such as magnesium sulphate, which is given intravenously and/or intramuscularly. In some cases, magnesium sulphate may be used before any convulsions occur, in order to prevent them from occurring.

HELLP Syndrome

The term ‘HELLP syndrome’ describes what is currently thought to be a form of severe pre-eclampsia. It involves:

  • Haemolysis (the breakdown of red blood cells in the circulation)
  • Elevated Liver enzymes (demonstrating early liver damage)
  • Low Platelets (platelets are needed to allow blood to clot properly and stop bleeding)

Doctors currently believe that the HELLP syndrome is not a separate condition from pre-eclampsia. The only proven treatment for this severe form of pre-eclampsia is urgent delivery of the infant.

Future Pregnancies

The risk of pre-eclampsia decreases with the second pregnancy with the same partner. Women who developed pre-eclampsia after 34 weeks of pregnancy have a very low risk of it returning in future pregnancies with the same partner. As a general rule, the milder the pre-eclampsia, the less likely it will develop again.