Understanding blood pressure

Why having high blood pressure can cause problems during labour


What is blood pressure?

As your heart contracts it pushes blood into your arteries, causing an increase in pressure – known as systolic pressure. As your heart relaxes and refills with blood, pressure falls – your diastolic pressure.


Blood pressure (BP) is the ratio of systolic pressure to diastolic pressure. A BP of 120/80 or less is normal for an adult. If you often have readings of 140/90 or above, your BP is high.

Why is high BP a problem in pregnancy?

High BP could be a sign of pre-eclampsia, a condition that occurs only during pregnancy. Not normally seen before the 20th week, it affects 1 in 10 pregnancies, although only 1 in 100 will develop complications from this.

Aside from high pressure and protein in the urine (which can be tested for by your midwife), signs include headaches, blurred vision, pain below the ribs on the right side, discolouration of the skin and eyes, vomiting and sudden swelling of hands and feet. If you have such symptoms, contact your midwife or GP.

If you have pre-eclampsia you’ll be monitored closely, drugs may be given to reduce blood pressure and in more severe cases your baby may be delivered early.


If pre-eclampsia isn’t treated, eclampsia may occur. This can cause seizures or strokes, and damage the brain, liver and kidneys if it goes untreated.

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