Pre-eclampsia: what it is and the warning signs to know

Pre-eclampsia is high blood pressure that affects other organs

Pre-eclampsia is diagnosed when blood pressure rises after 20 weeks of pregnancy and there are signs that other organs are affected: protein in the urine, blood tests showing strain on the kidneys or liver, or signs that the placenta is not working well, such as the baby growing more slowly than expected.

The problem is thought to begin in the placenta, which can release substances that affect the mother’s blood vessels and raise her blood pressure.

Many cases appear late in pregnancy and start mildly, but without treatment it can become serious for mother and baby. Raised blood pressure without the other signs is called gestational hypertension, and is watched closely because it can develop into pre-eclampsia.

Why blood pressure and urine are checked at every visit

Early pre-eclampsia rarely causes anything a woman would notice, so NICE advises measuring blood pressure and testing urine at every antenatal check, to find it before it causes harm.

The urine test looks for protein, which healthy kidneys keep in the blood. If a dipstick test shows protein, a sample is usually sent to the laboratory to measure it precisely.

One raised reading is not a diagnosis: stress, rushing or pain can raise blood pressure briefly, so it is measured again after a rest. If it stays raised, blood tests, a scan of the baby’s growth and more frequent checks may follow, sometimes as a day assessment in hospital.

If pre-eclampsia is confirmed, care usually moves to the hospital maternity team, with medicine to lower blood pressure and close monitoring of mother and baby. The condition usually settles once the baby and placenta are born, so the timing of birth becomes part of the plan, and sometimes an earlier birth is advised.

Who is more likely to develop pre-eclampsia

Any pregnant woman can develop pre-eclampsia, but some factors make it more likely. NICE groups them into two levels:

• Higher-risk factors: high blood pressure in a previous pregnancy, long-term kidney disease, an autoimmune condition such as lupus or antiphospholipid syndrome, type 1 or type 2 diabetes, or high blood pressure that was present before pregnancy.
• Moderate-risk factors: not having given birth before, being 40 or older, more than 10 years since your last pregnancy, a body mass index (BMI) of 35 or more at the early antenatal visit, a mother or sister who had pre-eclampsia, or expecting twins or more.

A risk factor does not mean pre-eclampsia will happen, and it can occur in women with none, so every pregnancy is checked.

For women with one higher-risk factor, or more than one moderate-risk factor, NICE advises low-dose aspirin every day, started at 12 weeks and continued until the birth, because it lowers the chance of pre-eclampsia. Like any medicine it can have side effects and does not suit everyone, such as some women with a bleeding disorder or aspirin allergy.

Do not start aspirin on your own because of what you read here. Whether to take it, the dose and when to stop are decided with your doctor.

Symptoms that can mean pre-eclampsia is getting worse

Symptoms usually mean the condition is affecting the body more, and they need assessing the same day.

The headache is usually severe and does not ease with your usual pain relief. Vision may blur, or flashing lights or spots may appear. Pain from the liver is felt just below the ribs, usually on the right, and is easily mistaken for heartburn. Vomiting and sudden swelling of the face, hands or feet are other signs.

Mild swelling of the feet and ankles is common in pregnancy, especially late in the day and in hot weather. The swelling that matters here comes on suddenly, or affects the face and hands.

Pre-eclampsia can also start after the birth

Pre-eclampsia does not always end with the birth. Blood pressure can stay high for a while, and in some women the condition begins after the baby is born, usually within days and occasionally weeks later.

Blood pressure is therefore checked after the birth, and the same warning signs apply in the weeks that follow. A severe headache in those early days is easy to blame on tiredness, and it still needs checking.

Some women go home on blood pressure medicine, which is reduced and stopped as readings settle, and blood pressure is rechecked at the postnatal review, about 6 to 8 weeks after the birth.

Pre-eclampsia also matters for the future. It is more likely to happen again in a later pregnancy, when aspirin is usually advised from 12 weeks, and it is linked with a higher chance of high blood pressure and heart disease later in life. Telling future doctors about it means your blood pressure can be checked regularly.