High blood pressure, or hypertension, does not usually make you feel unwell, but it can sometimes be serious in pregnancy.
Your midwife will check your blood pressure at all your antenatal (pregnancy) appointments.
If you are pregnant and have a history of high blood pressure, you should be referred to a specialist in hypertension and pregnancy to discuss the risks and benefits of treatment.
If you develop high blood pressure for the first time in pregnancy, you will be assessed in a hospital by a healthcare professional, usually a midwife, who is trained in caring for raised blood pressure in pregnancy.
What is high blood pressure
There are 3 levels of hypertension:
- 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
If you are already taking medicine for high blood pressure
If you're already taking medicine to lower your blood pressure and want to try for a baby, talk to your GP or specialist first. They may want to switch you to a different medicine before you get pregnant.
If you find out you're already pregnant, tell your doctor immediately. They may need to change your medicine as soon as possible.
This is because some medicines that treat high blood pressure may not be safe to take when you're pregnant. They can reduce the blood flow to the placenta and your baby, or affect your baby in other ways.
Your pregnancy appointments
It's important that your antenatal team monitors you closely throughout your pregnancy to make sure your high blood pressure is not affecting the growth of your baby and to check for a condition called pre-eclampsia. Make sure you go to all your appointments.
Your doctor or midwife will measure your blood pressure and check for protein in your urine. After 20 weeks of pregnancy, you may be offered a PlGF (placental growth factor) test to rule out pre-eclampsia.
During the first half of pregnancy, a woman's blood pressure tends to fall. This means you may be able to come off your medicine for a while. But this should only be done under your doctor's supervision.
Things you can try yourself to reduce high blood pressure
Keeping active and doing some physical activity each day, such as walking or swimming, can help keep your blood pressure in the normal range. Eating a balanced diet and keeping your salt intake low can help to reduce blood pressure.
There isn't enough evidence to show that dietary supplements – such as magnesium, folic acid or fish oils – are effective at preventing high blood pressure.
Pre-eclampsia is a condition that affects some pregnant women, typically after 20 weeks.
It is a problem with the placenta that usually causes your blood pressure to rise. If left untreated, pre-eclampsia can be dangerous for you and your baby.
Pre-eclampsia is more common if you had high blood pressure before becoming pregnant, if you had pre-eclampsia in a previous pregnancy, or if you have a family history of your mother or sister developing pre-eclampsia.
You can feel well if you have high blood pressure, so it is important to attend your regular check-ups to have your blood pressure and urine tested. Read more about pre-eclampsia and how pre-eclampsia is treated.
Labour and birth
If you're taking medicine throughout pregnancy to control your blood pressure, keep taking it during labour.
If you have mild or moderate hypertension, your blood pressure should be monitored hourly during labour. As long as your blood pressure remains within target levels, you should be able to have a natural vaginal birth.
If you have severe hypertension, your blood pressure will be monitored every 15 to 30 minutes in labour. Your doctors may also recommend your baby be delivered using forceps or ventouse, or by caesarean section.
After the birth, your blood pressure will be monitored.
If you had hypertension before you got pregnant, your treatment should be checked 2 weeks after your baby is born.
Check-ups after the birth
If you developed hypertension while you were pregnant and you're still taking medicine after the birth, you should be offered an appointment with a doctor 2 weeks after you transfer from hospital care to community midwives, or 2 weeks after the birth if you had a home birth.
This is to check whether your treatment needs to be changed or stopped.
Everyone with hypertension in pregnancy should also be offered an appointment with a GP or specialist 6 to 8 weeks after their baby is born.
This appointment is to check your blood pressure, and is separate from your 6-week postnatal check.
You should be able to breastfeed if you need to take hypertension medicine. Your treatment can be changed if needed, in agreement with your doctor.
Hypertension medicines can pass into breast milk. Most lead to very low levels in breast milk, and the amount taken in by babies is very small.
Most medicines are not tested during pregnancy or breastfeeding. Disclaimers or warnings in the manufacturer's information are not because of specific safety concerns or evidence of harm.
Find out about specific medicines and pregnancy at the website for Bumps (Best use of medicines in pregnancy).
Talk to your midwife or doctor about breastfeeding if you're taking medicine.