If you’re pregnant, you’ll be used to having your blood pressure closely monitored – your midwife will check it at every one of your antenatal appointments. This guide looks at the factors that can cause hypertension in pregnancy, the potential risks and complications, and the lifestyle adjustments you can make to safely lower high blood pressure.
The body goes through all sorts of changes during pregnancy, so it’s not surprising to learn that it’s perfectly normal for your blood pressure to change too.
Many women find that their blood pressure is lower in the first and second trimester. This is because an increase in the hormone, progesterone, relaxes the walls of your blood vessels, meaning the heart doesn’t have to work as hard to pump blood around the body. It’s usual for blood pressure to rise again in the third trimester, by which point your heart will be pumping around 45% more blood around your body.
In the UK, high blood pressure affects one in ten pregnant women. Sometimes high blood pressure is present before pregnancy. If that’s the case, and you’re taking medication to help control your blood pressure, talk to your doctor before trying for a baby. And if you find out you’re already pregnant, tell your doctor immediately, as not all medicines used to treat high blood pressure are safe to take during pregnancy.
Sometimes it can develop during the pregnancy. You are more likely to experience hypertension during pregnancy if you:
It’s also worth noting that pregnancy causes hormone shifts and psychological changes as well as physical ones. This can bring on stress, making high blood pressure harder to manage.
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Blood pressure is a good indicator of how your pregnancy is going. Your midwife will be looking for signs of pre-eclampsia: a potentially serious complication caused by a defect in the placenta, which supplies the baby with nutrients and oxygen from the mother’s blood. Another sign of pre-eclampsia is excess protein in the urine, which is why you’ll find yourself having to hand over a lot of urine samples throughout your pregnancy.
Different terms are used for high blood pressure that develops at different stages. Pre-existing hypertension is when you have high blood pressure before you got pregnant, or if it develops before you are 20 weeks’ pregnant. Gestational hypertension is high blood pressure that develops after 20 weeks of pregnancy. Having either pre-existing hypertension or gestational hypertension means you’re more likely to develop pre-eclampsia.
High blood pressure during pregnancy poses various risks to both mother and baby, including:
Women who had high blood pressure before pregnancy are at higher risk for related complications during pregnancy than those with normal blood pressure.
Whether you want to lower your blood pressure or maintain a healthy blood pressure reading, there’s a lot you can do to reduce the risk of complications during your pregnancy.
Doing some physical activity each day can help to keep your blood pressure in the normal range. Take a look at the NHS recommendations here, and consider a stress-relieving activity, such as yoga, to help you stay relaxed in the run-up to the birth.
There’s some confusion over how much you should eat during pregnancy, but the reality is you only really need an extra 200 calories a day in your final trimester. Eat a balanced diet and keep your salt intake low.
Smoking and drinking alcohol are known to raise blood pressure and can cause other complications during pregnancy. You should also talk to a doctor or pharmacist before taking over-the-counter medicines.
Your doctor will prescribe the safest medication at the most appropriate dose, so carry on taking it.
Finally, even if you feel perfectly healthy, it’s possible to develop gestational hypertension and pre-eclampsia without realising it. That’s why you really must attend all your antenatal appointments and allow your midwife to keep a close eye on your blood pressure.
Disclaimer: If you are concerned about your blood pressure, it is best to speak to your doctor. They can advise on the best way to manage your blood pressure.
Cardiovascular Physiology of Pregnancy, September 16, 2014 – https://www.ahajournals.org/circulationaha
High blood pressure in pregnancy, November, 2019 – https://action-on-pre-eclampsia.org.uk/high-blood-pressure-in-pregnancy
NHS, Pre-eclampsia, September 28, 2021 – https://www.nhs.uk/conditions/pre-eclampsia
NHS, Exercise in pregnancy, January 20, 2020 – https://www.nhs.uk/keeping-well-exercise
BBC, Women ‘unsure how much to eat while pregnant’, July 24, 2017 – https://www.bbc.com/health-40698876
NHS, Have a healthy diet in pregnancy, February 14, 2020 – https://www.nhs.uk/keeping-well-have-a-healthy-diet