Blood pressure during your pregnancy
This page contains affiliate links, which means we may earn a small amount of money if a reader clicks through and makes a purchase. All our articles and reviews are written independently by the Netmums editorial team.
During your pregnancy, your blood pressure will be checked regularly at routine GP and antenatal appointments. High blood pressure – or hypertension – can lead to a condition called pre-eclampsia so it's important to attend. Read on to find out what's normal, what's not and what to do about high or low blood pressure.
Why is your blood pressure monitored during pregnancy?
Your blood pressure describes how efficiently and healthily your blood is being pumped around your body.
It can also help to detect certain conditions or complications when you're pregnant.
That's why one of the first things your GP or midwife will do at every antenatal appointment is to check your blood pressure. Within minutes, you'll know whether it's low, normal or high. Appropriate treatment or further tests can then be carried out, if required.
FREE NEWBORN NAPPIES
Low blood pressure is fairly common and often harmless. If you have low blood pressure, you'll probably notice some dizziness or light-headedness during pregnancy.
High blood pressure – also referred to as hypertension – is estimated to affect 10% of all pregnancies. High blood pressure usually affects how your arteries and organs work, increasing your risk of heart problems, kidney and liver disease and having a stroke.
However, if you're pregnant, it can also be a sign of pre-eclampsia – a pregnancy condition that can be life-threatening for both you and the baby, if left untreated.
When and how is your blood pressure monitored?
If you've never had your blood pressure checked before getting pregnant, don't worry – it's painless and non-invasive.
A device (called a sphygmomanometer) will be strapped around your upper arm. This will be pumped up so that it gradually tightens around your arm, allowing your doctor or midwife to get your blood pressure reading on a dial or digital display.
The whole thing takes minutes to do and will be done at the start of every antenatal appointment you have, as well as during postnatal checks once the baby is born.
What's 'normal' when it comes to blood pressure?
A blood pressure reading takes into account the pressure on your arteries when your heart contracts or beats (systolic pressure) and the pressure on your arteries when your heart relaxes between beats (diastolic pressure).
This is why your blood pressure result will always be two different numbers, one higher and one lower ie 90/60 – your systolic pressure over your diastolic pressure. Blood pressure is measured in millimetres of mercury (Hg).
Your GP or midwife will tell you where your blood pressure lies on the scale of low to high but as a general guide:
- normal blood pressure will be between 90/60mmHg and 120/80mmHg
- high blood pressure will be between 140/90mmHg or higher
- low blood pressure will be between 90/60mmHg or lower.
What counts as high blood pressure?
The NHS splits up high blood pressure into three different levels. These are:
- mild – blood pressure between 140/90 and 149/99mmHg (millimetres of mercury); may be checked regularly but does not usually need treatment
- moderate – blood pressure between 150/100 and 159/109mmHg
- severe – blood pressure of 160/110mmHg or higher.
High blood pressure and pre-eclampsia
Pre-eclampsia – also called pregnancy-induced hypertension (PIH) or pre-eclamptic toxaemia (PET) affects about 10% of pregnancies. It can cause health problems for both you and your baby if it's undetected or untreated.
However, a rise in blood pressure in pregnancy is often an indicator of pre-eclampsia. As this will be regularly checked, your GP or midwife will be able to monitor and treat it.
You may be advised to have your baby early by C-section, too.
Find out more about pre-eclampsia here.
Treatment for high blood pressure
Depending on the severity of your high blood pressure and the stage of your pregnancy, your midwife will treat it with either:
- bed rest at home or at hospital
- medication to lower blood pressure – the most common medicines that are nationally recommended for use in pregnancy are labetalol, nifedipine and methyldopa
- a low dose of aspirin from 12 weeks of pregnancy and other medication such as vitamin D and folic acid (only when prescribed by your GP, midwife or obstetrician)
- or, referral to your nearest hypertension in pregnancy (HiP) clinic.
If you have pre-eclampsia, you may be booked in for an induction or C-section, ahead of your due date.
Treatment for low blood pressure
Low blood pressure is common in the first and second trimesters of pregnancy. Although it can cause dizziness and feeling faint, there's no treatment for it.
Your GP or midwife will probably recommend:
- sitting down when possible, for example on public transport and at work
- going from sitting to standing slowly and carefully (as this can cause dizziness if your blood pressure is low)
- eating and drinking water regularly
- not taking too hot showers or baths.
What happens to your blood pressure after having the baby?
If you've had low blood pressure during your pregnancy, it's highly likely that it'll return to normal towards your due date or once you've had the baby.
If you've had high blood pressure during your pregnancy, it'll be closely monitored before you're discharged.
Then you'll have to make sure that you:
- attend regular blood pressure checks with your midwife, health visitor and GP
- take prescribed medication.
What it means for your future health and future pregnancies
If you've had high blood pressure, you will have a higher risk of health complications in later life. However, the NHS advises that these risks can be reduced if you:
- do regular exercise – for example, 20 minutes fast walking a day
- eat a healthy, balanced diet
- don't drink too much alcohol (less than 14 units a week is advised)
- keep to a healthy weight for your height
- don't smoke cigarettes or take recreational drugs
- if you're diabetic, make sure you keep your blood sugars within your targets
- have your blood pressure and cholesterol checked at least once a year by your GP.
You're also likely to experience high blood pressure in future pregnancies.
According to the NHS:
'If you had high blood pressure before you became pregnant or had blood pressure problems in this pregnancy, you have a greater risk of similar complications in future pregnancies.
'The risk of complications in any future pregnancies depends on how severe your problem was and how many weeks pregnant you were when the high blood pressure started.'
If you've had high blood pressure in previous pregnancies and get pregnant again, make sure that you:
- see your GP as soon as possible and tell them about all your pregnancies
- ask your GP about starting low-dose aspirin (75mg daily) from 12 weeks’ gestation as this can reduce the risk of high blood pressure in pregnancy.
Related stories
Your week-by-week guide to pregnancy
