Pre-eclampsia is a condition that only occurs in pregnancy. The main feature is high blood pressure, but for a diagnosis of pre-eclampsia there must also be evidence that other organs are involved (such as protein in your urine).

The kidneys, liver, brain, placenta and blood clotting system are the organs most commonly involved.

The exact cause of pre-eclampsia is not understood, but in women who develop pre-eclampsia the placenta does not develop normally. So although a woman may not show signs of pre-eclampsia until after 20 weeks of pregnancy there may be tests that can be done as early as 12 weeks which show she is at risk of developing the condition. This would mean that those woman could be watched more closely and possibly even given treatment to delay or prevent the development of pre-eclampsia. 

Pre-eclampsia has been called many names over the years. Some of these are toxaemia, PET syndrome and HOP (which stands for hypertension, oedema and proteinuria). It is quite common, affecting up to 1 in every 14 pregnancies. In most cases pre-eclampsia is mild and normally has very little effect on pregnancy. However, in a few women (1 in every 100 pregnancies) it can develop into a serious illness.

What are the signs and symptoms of pre-eclampsia?

Pre-eclampsia often develops without any symptoms, and the first signs are usually a rise in blood pressure and the presence of protein in the urine. These signs are normally picked up during an antenatal visit.

In some women with severe pre-eclampsia, signs and symptoms may include:

  • ongoing, persistent or severe headache
  • changes in eyesight such as seeing spots, flashing lights or floaters, blurry vision
  • pain in your upper belly, tummy area or shoulder
  • sudden and new swelling in your face, hands, and eyes (some feet and ankle swelling is normal during pregnancy)
  • sudden weight gain (more than 1 kg in a week, or more than 3 kg in a month)
  • vomiting later in your pregnancy (not the morning sickness of early pregnancy)
  • difficulty breathing.
Seek medical advice immediately if you develop any of these symptoms during your pregnancy.

Who is at risk of developing pre-eclampsia?

The chance of developing pre-eclampsia is higher in women who:

  • have had pre-eclampsia before
  • are first time mothers or if it has been more than 10 years since their last baby
  • have a sister or mother who had pre-eclampsia
  • have high blood pressure before falling pregnant (pre-existing hypertension)
  • have certain medical conditions such as kidney disease or diabetes
  • are overweight
  • are 40 years or older
  • are expecting more than one baby (twins, triplets, etc)
  • had in vitro fertilisation.

Women who have an increased chance of developing pre-eclampsia may be prescribed a low dose of aspirin (100 milligrams) once a day from 12 weeks of pregnancy. 

However, most women who have these conditions will NOT develop pre-eclampsia. They may, however, be suitable for aspirin treatment and should have their blood pressure taken carefully at each visit. They should also be on the watch for any of the signs or symptoms of pre-eclampsia and report these to their lead maternity carer.

Many of the women who develop pre-eclampsia will have none of these risk factors, so all pregnant women still need to have their blood pressure and urine checked each visit.

How can pre-eclampsia affect my baby or me?

Having pre-eclampsia can be a concern for both the mother and the baby. The more severe your pre-eclampsia and the earlier it occurs in your pregnancy, the greater the risks for you and your baby. 

Risks to you as the mother include:

  • damage to your kidneys or liver
  • a greater chance of having a stroke
  • an increased risk of blood clotting problems
  • a chance of developing  placental abruption (risk of severe bleeding from your placenta)
  • developing eclampsia (having seizures).

Risks to your baby include:

  • poor growth
  • an increased risk of premature birth (born before 37 weeks)
  • an increased chance of stillbirth.  

How is pre-eclampsia treated?

Once a woman has developed pre-eclampsia the condition will not go away until after the baby is born. Treatment for pre-eclampsia is aimed at prolonging the pregnancy until the baby is big enough and developed enough to be born safely without too much risk to the mother or the baby during that time. If the baby does need to be born early because of complications there are treatments that can decrease the risks for the baby from being born prematurely. See premature birth.

Treatment options include:

Rest and gentle activity

Traditionally, continuous bed rest was recommended for all women with pre-eclampsia, but research has not shown a benefit from this. Actually, ongoing bed rest and lack of activity can increase your risk of blood clots. For most women, continuous bed rest is no longer recommended but it is advisable to limit your activity, avoid stress and rest now and again, throughout the day. 


Severe pre-eclampsia may require that you be hospitalised. In the hospital, your doctor will perform regular tests to monitor your baby's well-being and measure the volume of amniotic fluid. A lack of amniotic fluid is a sign of poor blood supply to the baby.



Aspirin has been shown to decrease the chances of a woman developing pre-eclampsia by about 10%. In other words, it will stop 1 out of 10 women from getting pre-eclampsia. The dose used is much smaller than the dose you would use for treating a headache and is called low-dose aspirin.

Although aspirin is very safe at low doses, no medications should be used in pregnancy unless there is a good reason. If you think you might benefit from aspirin treatment you should talk to your doctor. Aspririn needs to be started before 20 weeks and ideally at 12 weeks to have the best effect.

Aspirin does not seem to be of any benefit once pre-eclampsia has been diagnosed and is usually stopped before delivery.


If your blood pressure rises too high you will normally be prescribed medication to lower it (called antihypertensives). Your doctor will choose an antihypertensive that is considered safe in pregnancy.

Remember, having your blood pressure lowered by a hypertensive does not mean your pre-eclampsia has gone. The blood pressure medication keeps you safe while you wait for the baby to becomes more mature and better able to cope with being born.

Examples of antihypertensives that are commonly used to treat pre-eclampsia include:

To ensure that the medication is working, your doctor will monitor your blood pressure regularly and may adjust your medication dose if necessary.

If your blood pressure drops too low, then the blood flow to the placenta and the baby may fall too low, and the baby can become distressed, so don't be alarmed if your doctors allow your blood pressure to remain just above the normal range.


If you're diagnosed with pre-eclampsia near the end of your pregnancy, your doctor may recommend inducing labour right away. 

If delivery is being considered and baby is premature (particularly before 32 weeks) then the mother will usually be given 2 steroid injections 12-24 hours apart, which help to mature the baby’s lungs. Whenever possible the birth will be delayed for 24 hours to enable the steroids to be effective. 

If you are still more than a month away from your due date, or if there are signs that the baby may not cope well with a labour, a caesarian section will be recommended as the safest way to deliver your baby.

In general, if you are close to your due date it is possible to have a normal birth after labour is induced. The baby's heart rate will need to be monitored closely once contractions start because the baby is often smaller than usual.

During labour, you may be offered an epidural, which is usually used for pain relief in labour but also helps to keep your blood pressure under control.

You may also be given magnesium sulphate intravenously to prevent seizures. Magnesium also crosses over to the baby and helps protect the baby.

How are woman with pre-eclampsia monitored

If you develop pre-eclampsia you will probably be admitted to hospital for close observation. Sometimes you will be given medication to lower your blood pressure, but it is important not to lower the blood pressure too much or too suddenly as this can cause distress to the baby.

  • Your blood pressure will be checked about every four hours
  • Blood tests and urine protein levels will be regularly tested to check on your kidney function.
  • You will usually be may be offered an ultrasound scan to look at how your baby is growing and to check the blood flow from the placenta to the baby.
  • You may be prescribed medicines to control your blood pressure.

What happens after pregnancy

Pre-eclampsia always goes away after birth but not immediately. The condition may become more severe for the first few days and this is a time when you will need close supervision. This used to be the time when the most serious complications occurred.

This can also be a frustrating time for the mother and her family because she may be separated from her baby for a few days if the mother is unwell and the baby is in the neonatal unit.

If you have had severe pre-eclampsia, you may be asked to continue your blood pressure lowering medication and you will be monitored for the first few days after delivery. You may also need to stay in hospital for a few days so that you and your baby can be monitored.  

If you have had severe pre-eclampsia, some hospitals will offer you an appointment to see a specialist a few months after delivery to discuss what has happened and what may happen in future pregnancies. Usually, the pre-eclampsia is not as severe in the next pregnancy but there may be blood tests that need to be done to look for medical conditions which could result in another complicated pregnancy.

Learn more

Pregnancy and High Blood Pressure Patient Info, UK
Pre-eclampsia – Information for pregnant women Auckland District Health Board, 2016

Credits: Health Navigator Editorial Team. Reviewed By: Dr J Tuohy, University of Auckland (7 October 2016).