Normal blood pressure range during pregnancy chart

Your midwife or doctor will check your blood pressure at every antenatal appointment. Making sure your blood pressure is at a healthy level is an important part of looking after you and your baby during pregnancy. It's perfectly normal for your blood pressure to change a little during pregnancy (Bramham et al 2013).

The hormone progesterone relaxes the walls of your blood vessels. This may make your blood pressure fall during your first trimester and second trimester (Bramham et al 2013, Murray and Hassall 2014, NHS 2018, SOMANZ 2014). You may find you feel faint if you stand for too long or get up quickly (NHS 2017).

Your blood pressure is at its lowest in mid-pregnancy and starts to rise gradually again from 24 weeks (Murray and Hassall 2014). By this time, you'll have made an extra litre of blood, which your heart has to pump around your body (Murray and Hassall 2014).

If all is well, your blood pressure will return to its pre-pregnancy levels in the last few weeks before your baby is born (Bramham et al 2013, Murray and Hassall 2014).

Your midwife or doctor will use a small monitor to measure and record your blood pressure at every antenatal check-up (RANZCOG 2016). Before your caregiver measures your blood pressure, she'll ask you to sit down and remove any tight clothing from your arm. Then she’ll wrap a cuff around your arm above your elbow, and pump air into it. The cuff inflates and briefly stops the blood flow in the main blood vessel in your arm. It will feel tight, but it shouldn't hurt. Then, the air in the cuff is slowly released. The cuff is attached to the monitor, which calculates your blood pressure and shows a reading. The reading will show two figures that look like a fraction: for example, 110/70. The first, or top, number tells your doctor or midwife about your blood pressure as your heart pushes the blood round your body (systolic blood pressure). The second, or bottom, number is your blood pressure when your heart relaxes between beats (diastolic). What's normal for you could be different from other mums-to-be, so it's best not to compare results. The average blood pressure range if you're healthy is between 110/70 and 120/80, although this varies a lot in pregnancy.

Your doctor or midwife will tell you if your numbers are high. She’ll diagnose high blood pressure if your top figure (systolic) is 140 or higher or your bottom figure (diastolic) is 90 or more (NHS 2018, SOMANZ 2014).

There are three grades of high blood pressure (hypertension):

mild hypertension is when your top figure is between 140 and 149, or your bottom figure is between 90 and 99
moderate hypertension is when your top figure is between 150 and 159, or your bottom figure is between 100 and 109
severe hypertension is when your top figure is 160 or more, or your bottom figure is 110 or more
(NCCWCH 2010, SOMANZ 2014)

During an antenatal appointment, if your doctor or midwife discovers you have high blood pressure, she’ll ask you to come back and have it checked again, or go to your maternity unit for monitoring. If it’s severe, you may be admitted to hospital until it falls. High blood pressure has different names, depending on what stage in your pregnancy you develop it:

Before you're 20 weeks pregnant, if you have high blood pressure, it’s called chronic hypertension or pre-existing high blood pressure. This means you probably had high blood pressure before you became pregnant. You'll only know for sure if this is the case if your blood pressure stays high after your baby is born.
After 20 weeks, high blood pressure is called gestational hypertension. This is the name for high blood pressure that develops only during pregnancy.
(DH 2018, NCCWCH 2010)

Gestational hypertension isn't usually a problem, although you’ll be referred to hospital for more testing and monitoring, just in case. Measuring your blood pressure is a way of telling how well your pregnancy is going. Your doctor or midwife will be watching for signs of a potentially serious condition called pre-eclampsia, particularly later on in your pregnancy (NCCWCH 2010, NHS 2015).

Pre-eclampsia isn't fully understood, but it's thought it to happen when the placenta isn’t working as well as it should (NCCWCH 2010, NHS 2015, 2018, RCOG 2012). This can lead to high blood pressure and other problems. Your caregiver may test your urine as well as your blood pressure. Protein in your urine and high blood pressure are both signs of pre-eclampsia (NCCWCH 2010, NHS 2015, RCOG 2012).

Having either pre-existing hypertension or gestational hypertension does mean you’re more likely to develop pre-eclampsia (RCOG 2012). It doesn't mean you’ll definitely get it, though.

You’re more at risk of pre-eclampsia if you develop gestational hypertension before 35 weeks. If this happens to you, your doctor or midwife should monitor you more often to be on the safe side (NCCWCH 2010, NHS 2015).

You may develop gestational hypertension and pre-eclampsia without realising it. In fact, you may feel perfectly well. That's why it's important to go to all your antenatal appointments so your caregiver can regularly check your blood pressure and urine.

You could ask your doctor or midwife to explain the symptoms to watch out for. And if you feel unwell or odd for no obvious reason between antenatal appointments, contact your caregiver. Occasionally, pre-eclampsia can develop quickly and it's important to get medical help straight away (NCCWCH 2010, NHS 2015, RCOG 2012).

Blood pressure usually falls immediately after you’ve given birth. Then it rises again, peaking three to six days later. That’s the case for women who had normal blood pressure during pregnancy, as well as those with high blood pressure (Bramham et al 2013).

It’s quite normal for your blood pressure to fluctuate a bit in the weeks after the birth. If you had high blood pressure when you were pregnant, it will probably be back to normal within a few weeks of having your baby (NCCWCH 2010, NHS 2018, Smith et al 2013).

Your blood pressure will be monitored during labour and after the birth (NHS 2018). After that, if you had gestational hypertension or chronic hypertension, a midwife will check it daily for the first few days, then at least once between days three and five after the birth (NCCWCH 2010).

If your blood pressure stays high, you may need to take medication to control it for a few months after you've had your baby (NCCWCH 2010). This is just to be on the safe side. Don't worry if you intend to breastfeed. There are plenty of medications for high blood pressure that are safe to take while breastfeeding (NCCWCH 2010, Smith et al 2013).

Once your midwife has discharged you, you’ll still need to have your blood pressure checked. So make an appointment with your GP so that she can care for you and make any necessary changes to your medication.

If you had pre-existing high blood pressure, it’s unlikely to go down after you've had your baby. You may continue to need medication (NCCWCH 2010, Smith et al 2013).

Keeping active and eating well during your pregnancy will help you stay healthy whatever your blood pressure level. If you have high blood pressure in pregnancy, it helps to keep your salt intake low, as this can reduce blood pressure (NCCWCH 2010, NHS 2018).

Find out more about:

Bramham K, Nelson-Piercy C, Brown MJ. 2013. Postpartum management of hypertension. BMJ 346:f894. www.bmj.com [Accessed June 2018]

DH. 2018. Pregnancy care: clinical practice guidelines. Department of Health. Canberra: Department of Health. www.health.gov.au [Accessed June 2018]

Murray I, Hassall J. 2014. Change and adaptation in pregnancy. In: Marshall JE, Raynor MD. eds. Myles Textbook for Midwives. 16th ed. Edinburgh: Churchill Livingstone, 143-77

NCCWCH. 2010. Hypertension in pregnancy: the management of hypertensive disorders during pregnancy. Updated January 2011. National Collaborating Centre for Women's and Children's Health, NICE clinical guideline, 107. London: RCOG Press. www.nice.org.uk [Accessed June 2018]

NHS. 2015. Pre-eclampsia. NHS Choices, Health A-Z. www.nhs.uk [Accessed June 2018]

NHS. 2017. Low blood pressure (hypotension). NHS Choices, Health A-Z. www.nhs.uk [Accessed June 2018]

NHS. 2018. High blood pressure (hypertension) and pregnancy. NHS Choices, Health A-Z. www.nhs.uk [Accessed June 2018]

RANZCOG. 2016. Antenatal care during pregnancy. Royal Australian and New Zealand College of Obstetricians and Gynaecologists, Patient information pamphlet. www.ranzcog.edu.au [Accessed June 2018]

RCOG. 2012. Pre-eclampsia: information for you. Royal College of Obstetricians and Gynaecologists, Patient information leaflet. www.rcog.org.uk [Accessed June 2018]

Smith M, Waugh J, Nelson-Piercy C. 2013. Management of postpartum hypertension. TOG 15(1):45-50

SOMANZ. 2014. Guideline for the management of hypertensive disorders of pregnancy. Updated June 2015. Society of Obstetric Medicine of Australia and New Zealand. www.somanz.org [Accessed May 2018]

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