What is blood pressure?

High blood pressure in pregnancy is a common medical problem that usually disappears once the baby is born. In some cases, it can signal a serious condition called pre-eclampsia.

Your blood pressure is a measure of how strongly your blood pushes against the walls of the blood vessels.

It’s normally recorded in 2 numbers:

• The top number (systolic) is the pressure when the heart is pumping.
• The bottom number (diastolic) is the pressure in between each beat.

When you are pregnant, your blood pressure is considered high if the top number is 140 or more or the bottom number is 90 or more (described as “140 over 90”). High blood pressure is sometimes called hypertension.

Different types of high blood pressure in pregnancy

There are 3 types of high blood pressure during pregnancy:

• Chronic hypertension: This is when you already had high blood pressure before you fell pregnant. Chronic hypertension also refers to when your high blood pressure is diagnosed in the first 20 weeks of pregnancy. Some people with chronic hypertension may develop pre-eclampsia when they are pregnant.
• Pregnancy-induced hypertension: This is high blood pressure diagnosed after 20 weeks of pregnancy. It is also called ‘gestational hypertension’.
• Pre-eclampsia: Pre-eclampsia is a serious condition that only occurs in pregnancy. As well as high blood pressure, it can also affect the kidneys, liver, blood and brain.

What are the risk factors for high blood pressure during pregnancy?

Anyone can develop high blood pressure during their pregnancy, but you are at increased risk if:

• you have had pre-eclampsia before
• your close relatives have had pre-eclampsia
• you have a medical condition such as kidney disease, diabetes or chronic hypertension
• you are older than 40 years of age
• you are obese
• you are having more than one baby

Can high blood pressure affect my baby?

High blood pressure in pregnancy can prevent blood from flowing to the placenta. Because the baby doesn’t get enough nutrients or oxygen, untreated high blood pressure can put them at higher risk of complications such as:

• being low birth weight
• preterm labour and/or premature birth
• placental abruption
• stillbirth

For this reason, it’s very important that high blood pressure is picked up early and treated.

How does high blood pressure in pregnancy affect me?

High blood pressure in pregnancy increases your risk of developing gestational diabetes.

If you experience high blood pressure in pregnancy, you are more likely to have problems with high blood pressure and heart disease in later life.

How is high blood pressure in pregnancy treated?

Your doctor or midwife will check your blood pressure regularly. If you have high blood pressure, it is important to:

• quit smoking
• eat a healthy diet
• exercise regularly
• make sure you are a healthy weight

If you already take medicines regularly to control your blood pressure, it’s important to talk to your doctor about what medicines are safe to take during pregnancy.

There are medicines your doctor can prescribe for pre-eclampsia. Both you and your baby will also need to be closely monitored. Remember that pre-eclampsia can become worse very quickly. If this happens, you may need to go to hospital or give birth to your baby early.

How does high blood pressure impact labour and birth?

If you have high blood pressure, both you and your baby will be closely monitored during the pregnancy. During labour, the baby’s heart rate will be continuously monitore. You may have an intravenous drip to give you fluid and medicines. If your condition seems to be worsening during labour, you may need an emergency caesarean.

If you have pre-eclampsia, your doctor may recommend that you have your baby in a large maternity hospital so you and your baby can get expert care if you need it. It may mean the baby is born early or is smaller than expected.

Will my blood pressure stay high after the birth?

High blood pressure in pregnancy usually disappears once the baby is born. However, there may still be some complications during the first few days after the birth. You will need to be monitored carefully for several weeks.

If you have high blood pressure due to another condition (chronic hypertension), you will need to see your doctor to make sure your blood pressure returns to safe levels.

Are there any implications for future pregnancies?

Having high blood pressure in pregnancy doesn’t necessarily mean you will develop high blood pressure in future pregnancies. However, your risk is increased, especially if you have a medical condition such as hypertension, kidney disease, diabetes or lupus.