What is blood pressure?

High blood pressure (also known as ‘hypertension’) in pregnancy is a common medical problem that usually disappears after the birth. 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 heartbeat.

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

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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 pregnancy. Chronic hypertension increases your risk of developing pre-eclampsia during pregnancy. Hypertension is also considered ‘chronic’ if you were diagnosed in the first 20 weeks of pregnancy.
• Pregnancy-induced hypertension (gestational hypertension) — This is high blood pressure diagnosed after 20 weeks of pregnancy.
• Pre-eclampsia — Pre-eclampsia is a serious complication of pregnancy. It causes high blood pressure as well as affecting one or more organs including the liver, kidneys, blood and brain.

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

Anyone can develop high blood pressure during 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 living with overweight or obesity
• you are having more than one baby
• you conceived with in vitro fertilisation (IVF)

Can high blood pressure affect my baby?

High blood pressure in pregnancy can prevent enough blood from flowing to the placenta. This may mean that your baby doesn’t get enough nutrients or oxygen. Untreated high blood pressure can increase their risk of complications such as:

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

To reduce the chance of complications, it’s important that high blood pressure is identified early and treated.

How does high blood pressure in pregnancy affect me?

High blood pressure in pregnancy increases your risk of developing pre-eclampsia and its associated complications.

If you experience high blood pressure in pregnancy, you are more likely to develop high blood pressure or 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, you can help manage it by:

• quitting smoking
• eating a healthy diet
• exercising regularly
• maintaining a healthy weight

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

There are medicines your doctor can prescribe to reduce your chance of developing pre-eclampsia. Ask your doctor if they may be right for you.

Both you and your baby will also need to be closely monitored. Remember that pre-eclampsia can worsen quickly. If this happens, you may need to be monitored in hospital or birth your baby early.

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How does high blood pressure impact labour and birth?

If you have high blood pressure, both you and your baby will be monitored closely throughout pregnancy.

During labour, the baby’s heart rate may be continuously monitored. Your doctor may recommend an intravenous drip to give you fluid and medicines. If your condition seems to be worsening during labour, your doctor may suggest an emergency caesarean to birth your baby quickly.

If you have pre-eclampsia, it’s usually best to plan to birth in a large maternity hospital. This is so you and your baby can get expert care if you need it, for example, if your baby ends up being premature or smaller than expected.

Will my blood pressure stay high after the birth?

Hypertension that starts during pregnancy usually resolves after your baby’s birth. However, there may still be some complications during the first few days after the birth. You should be monitored carefully for several weeks.

If you had pre-existing chronic hypertension, you should see your doctor to check whether you need ongoing treatment.

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 obesity, kidney disease or diabetes.

Resources and support

The Royal Women's Hospital has information on high blood pressure and preeclampsia.

Other languages

The Society of Obstetric Medicine of Australia and New Zealand has information sheets about pre-eclampsia and other pregnancy topics in many community languages.