High blood pressure in pregnancy

If you have high blood pressure, there is no reason why you can't have a perfectly healthy pregnancy with the right treatment and support. 

Some women develop high blood pressure during pregnancy and some have high blood pressure before becoming pregnant. These both bring a slightly higher risk of complications than if your blood pressure is normal, but you will have careful monitoring to make sure you’re given the treatment and advice you need at the right time.

After your pregnancy, you could have a higher risk of high blood pressure and the problems it causes later in life. It’s important to lead a healthy lifestyle and see your GP every five years for a blood pressure check.

If you are planning to get pregnant and you have high blood pressure, speak to your doctor. If your blood pressure is well controlled they can give you the right treatment and support. If it is not well controlled it will be safer to wait until it is brought under control.

High blood pressure before getting pregnant

If you have high blood pressure before becoming pregnant, or that is found in the first 20 weeks of pregnancy, this is thought of as long-term or chronic hypertension (high blood pressure). This carries a slightly higher risk of complications during pregnancy than for women with normal blood pressure.

Your team will keep a close eye on you throughout your pregnancy to make sure your baby is developing normally and so they can spot any signs of complications early. They might ask you to record your blood pressure at home with 24 hour ambulatory home monitoring, and will let you know how often you should come in to the clinic.

Ideally, your doctor will want to keep your blood pressure below 150/100mmHg. They will give you lifestyle advice and might consider medications to lower your blood pressure.

You should be advised to take an aspirin a day when you first check in to the antenatal clinic.

Medications for high blood pressure during pregnancy

The role of blood pressure medicines is to lower the risk of heart attack or stroke in the mother. Women of childbearing age have only a very minor risk of heart attacks or strokes, so your doctor will probably only consider medications if your systolic blood pressure (the top number) is consistently over 160mmHg, to avoid giving any unnecessary medications to the developing baby. 

Some medications are thought to be safe while for others there is some evidence that they could affect the baby or there isn’t enough evidence to know for sure. ACE inhibitors and angiotensin II receptor blockers could reduce blood flow to the placenta, and diuretics and beta blockers may also need to be avoided. Your doctor will consider carefully which medications to use.

• If you are planning to get pregnant and you are taking medications to control your blood pressure, speak to your doctor in case you need to change medications.
• If you are already pregnant and you’re taking blood pressure medications, see your doctor as soon as possible as you might need to switch to a different medication.

 You might be advised to stop taking your medications while you are pregnant, but start them again afterwards.

Changes to your lifestyle

It’s important to keep active and eat a healthy diet which is low in salt to keep your blood pressure under control, but avoid going on a rigorous diet. NHS Choices have more in eating healthily during pregnancy.

After your pregnancy

You should also be offered an appointment with a doctor at your 6-week post-natal check. They will measure your blood pressure and review your medications and aim to keep your blood pressure below 140/90mmHg.

Developing high blood pressure during pregnancy

If your blood pressure rises to 140/90mmHg or more after 20 weeks of pregnancy, this could be due to one of two conditions, gestational hypertension (sometimes called pregnancy-induced hypertension) or pre-eclampsia.

Raised blood pressure on its own, with normal tests for kidney and liver function, is considered gestational hypertension. It’s usually mild and doesn’t cause problems. You will need to go to the clinic for regular check-ups in case of any changes, and you might be asked to record your blood pressure at home with 24 hour ambulatory home monitoring.

If high blood pressure develops later on, after 32 weeks, this puts you at a higher risk of complications, including pre-eclampsia, which can be serious and needs treating.

Treatments for gestational hypertension

You should be advised to take an aspirin a day when you are first diagnosed with high blood pressure.

Whether you need treatment for high blood pressure, and which treatments you are given, will depend on whether you have any of the other risk factors for pre-eclampsia and your blood pressure readings during pregnancy:  

• 140/90mmHg – 149/99mmHg  – you will need regular blood pressure checks, urine tests and blood tests, but this doesn’t normally need treating.
• 150/100mmHg – 159/109mmHg  – you might need medications for your blood pressure, as well as regular blood pressure checks and urine and blood tests.
• 160/110mmHg or higher – You may need medications to lower your blood pressure, frequent blood pressure checks and urine and blood tests, and you might need to stay in hospital for a short while until your blood pressure is under control

If you do need medications for high blood pressure, your doctor will consider which ones are safe to use and the possible side effects.

After your pregnancy

Your blood pressure should return to normal after your pregnancy. You should also be offered an appointment with a doctor soon afterwards in case you need to keep taking any blood pressure medications, and because blood pressure can also sometimes rise after pregnancy. 

What is pre-eclampsia?

Pre-eclampsia is where high blood pressure develops during pregnancy along with protein in the urine, which are not seen with gestational hypertension. It can affect the function of the liver and kidney and reduce the number of platelets in the blood – the tiny blood cells which control blood clotting. Pre-eclampsia usually occurs in the second half of pregnancy, after 28 or 30 weeks, but can be earlier.

Pre-eclampsia usually doesn’t cause any problems, but without treatment, it can lead to complications for the mother and baby. This is why you will have your blood pressure monitored throughout your pregnancy, as well as urine tests to look for protein, and blood tests to look for other signs of pre-eclampsia. 

What causes pre-eclampsia isn’t fully understood, but is thought to be due to a problem with the development of the placenta.

You will be more at risk of developing pre-eclampsia if:

• you already have high blood pressure
• you have kidney disease, diabetes or an autoimmune disorder
• you had pre-eclampsia or another high blood pressure disorder of pregnancy in the past
• it’s your first pregnancy
• you are 40 or over
• your last pregnancy was over 10 years ago
• you’re overweight with a BMI over 35
• you have family history of pre-eclampsia
• you’re carrying more than one baby

If you are at higher risk or pre-eclampsia, you should be advised to take an aspirin a day (75mg) from 12 weeks of pregnancy.

What are the signs and symptoms of pre-eclampsia?
You will usually need a blood pressure check to spot pre-eclampsia, but it can sometimes have the following signs and symptoms:

• severe headaches
• problems with your vision, such as blurring or flashing before your eyes
• severe pain just below the ribs
• vomiting
• sudden swelling in the face, hands and feet
• severe heartburn

This video from the NHS explains more about pre-eclampsia and the warning signs.

Complications of pre-eclampsia
If untreated, pre-eclampsia can develop into eclampsia, where the mother has fits and seizures. It can also lead to stroke, kidney and liver problems, blood-clotting disorders, fluid on the lungs, and premature birth. 

Pre-eclampsia affects the placenta which can affect the baby’s growth because not as much oxygen and nutrients are being delivered. In the worst cases it can lead to stillbirth.

Treatments for pre-eclampsia
If you have pre-eclampsia, you will need to have regular appointments or stay in hospital for a while so that you can be closely monitored. You should be referred to a specialist obstetric unit where you will have blood pressure checks, urine tests and blood tests so that your team can change your treatment if there are any changes, and you will also have ultrasound scans to check the baby’s growth.

You’ll be given medications to lower your blood pressure, usually labetalol, nifedipine or methyldopa, and you might need to deliver the baby early.

After your pregnancy
Your team will continue to monitor you after giving birth so that they can make the right adjustments to your treatment.

Is it safe to breastfeed while taking blood pressure medications?

Many blood pressure medicines are thought to be safe during breastfeeding, including nifedipine, methyldopa and hydralazine.

For others, there is not enough evidence to know whether they are suitable, either because they could be passed on to the baby or they could affect the production of breast milk. These include angiotensin receptor blockers, ACE inhibitors, the calcium-channel blocker amlodipine, beta blockers and diuretics.

You will probably only be offered medications to lower your blood pressure if your systolic blood pressure (the top number) is over 160mmHg. Speak to your doctor about the right medications to use if you’re planning to breast feed your baby.

Your long-term health
If you have had high blood pressure or pre-eclampsia during pregnancy, you’re more likely to have high blood pressure in the future and the complications it causes, including heart disease and stroke. So it’s important to look after your health in the long term and get any help or advice you need.

Leading a healthy lifestyle with a healthy diet and exercise will help you to keep your blood pressure in check. Have a blood pressure check at least every five years so that you can get any advice you need, and can start taking medications if you need to.

Read more
NHS Choices have more information on high blood pressure in pregnancy.

Professor Gareth Beevers, Trustee and Emeritus Professor of Medicine, and Mr David Churchill, consultant obstetrician discuss how raised blood pressure before becoming pregnant can affect the mother and baby and what the team looking after her will do to help, in our summer 2017 issue of Positive Pressure.

Two important studies published in 2017 showed that high blood pressure during pregnancy can put women at higher risk of high blood pressure and the problems it causes later on in life, highlighting the need for careful monitoring and advice throughout their lives from their GP.

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