Pre-eclampsia | Pēhanga toto i te hapūtanga

Key points about pre-eclampsia

  • Pre-eclampsia (pēhanga toto i te hapūtanga) is a serious condition for you and your baby. The main feature is high blood pressure, but for diagnosis there must be evidence other organs are involved (eg, protein in your urine).
  • If you develop it, you and your baby will be closely monitored for the rest of your pregnancy and may have to deliver early. 
  • Pre-eclampsia often develops without any symptoms. If you have any of the warning signs or symptoms listed below, see your pregnancy care provider straight away.
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Pre-eclampsia is a condition that only occurs during pregnancy and up to 2–3 weeks after delivery.

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. Your kidneys, liver, brain, placenta and blood clotting system are the organs most commonly affected by pre-eclampsia. 

Pre-eclampsia often develops without any symptoms. The first signs are usually a rise in blood pressure and the presence of protein in your 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 or 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 the symptoms above during your pregnancy.

Video: What is pre-eclampsia and what are the warning signs?

Midwife Suzanne Barber explains the warning signs of pre-eclampsia. Click the arrow in bottom left corner to play. This video may take a few moments to load.

(NHS, UK, 2015)

The cause of pre-eclampsia is not fully understood, but in women who develop pre-eclampsia the placenta does not develop normally.

Although you may not show signs of pre-eclampsia until after 20 weeks of pregnancy, it is possible to identify some women who are at greater risk of developing the condition early in pregnancy. Treatment early in pregnancy will stop some women developing pre-eclampsia. If you are at risk, you will be watched more closely to delay or prevent the development of 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 your last baby
  • have a sister or mother who had pre-eclampsia
  • have high blood pressure before getting 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 (IVF)
  • have low levels of placental hormones in the first trimester of pregnancy.

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

Most women who have these conditions do NOT develop pre-eclampsia. You may, however, be suitable for aspirin treatment and should have your blood pressure taken carefully at each visit. You should also be on the watch for any of the signs or symptoms of pre-eclampsia and report these to your LMC.

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

Having pre-eclampsia can be a concern for both you and your baby. The more severe your pre-eclampsia is 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.  

Once you have developed pre-eclampsia, it won’t go away until after your baby is born. To put this another way, there is only one cure for pre-eclampsia and that is the birth of your baby. If you develop pre-eclampsia, you will be referred to an obstetrician or specialist for tests and checks and may require admission to the hospital.

Treatment for pre-eclampsia is aimed at managing the complications of pre-eclampsia so your pregnancy can continue safely. Prolonging the pregnancy means that your baby continues to grow and develop.

If your baby does need to be born early because of complications there are treatments that can decrease the risks for your baby from being born prematurely. Read more about premature birth.

Treatment options for pre-eclampsia 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. So for most women, continuous bed rest is no longer recommended but it is a good idea to limit your activity, avoid stress and rest now and again throughout the day. 


Severe pre-eclampsia may require you to say in hospital. In the hospital, your doctor will do regular tests and checks to monitor your wellbeing and the wellbeing of your baby.

There are two main reasons for being admitted to hospital. The first is because tests like blood pressure need to be done every few hours. The second is that you or your baby could develop complications quickly and need urgent care. 

How is pre-eclampsia monitored?

Sometimes you will be given medication to lower your blood pressure, but the aim will be to not lower the blood pressure too much or too suddenly as this can cause distress to your baby.

  • Your blood pressure will be checked about every 4 hours.
  • Blood tests and urine protein levels will be regularly tested to check on your kidney function.
  • You may be offered an ultrasound scan to look at how your baby is growing and to check the blood flow from the placenta to your baby.
  • You may be prescribed medicines to control your blood pressure.



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


Some women, particularly those with low calcium diets, may also be prescribed calcium.


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.

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 your baby to become more mature and better able to cope with the stress of delivery.

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 your baby may fall, and your baby can become distressed. This is why your doctor allows your blood pressure to remain just above the normal range.

Some women with high blood pressure before pregnancy may be on treatment with a group of medications called ACE inhibitors. Women who are planning a pregnancy and using ACE inhibitors should seek advice about changing to a different blood pressure medication. 

Antenatal corticosteroids

If delivery is planned and your baby is premature (particularly before 32 weeks), you will usually be given 2 steroid injections 12–24 hours apart, which help to mature your baby’s lungs. Whenever possible the birth will be delayed for 24 hours to give the steroids time to be effective. 

Magnesium sulphate

You may also be given magnesium sulphate through your vein to prevent seizures. Women who require magnesium treatment have developed severe pre-eclampsia and will almost always need to give birth to their baby within the next 24 hours. Magnesium also crosses over to your baby and helps to protect the baby's brain after birth.


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

If you are still more than a month away from your due date, or if there are signs that your baby may not cope well with a labour, a caesarean 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.

Pre-eclampsia goes away after birth but may take 2–3 weeks to settle down. It can become more severe for the first few days, so you will need close supervision for 2 or 3 days after giving birth. This used to be the time when the most serious complications occurred.

This can be a frustrating time for you and your family/whānau because you may be separated from your baby for a few days if you are unwell and your baby is in the neonatal unit.

If you have had severe pre-eclampsia, your blood pressure may not come back to normal for a few weeks, so you may need to continue your blood pressure lowering medication for a while. 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.

The following information on hypertension in pregnancy and postpartum(external link) is taken from Auckland Regional HealthPathways, NZ, accessed July 2020:

Red flags

  • New onset hypertension after 20 weeks.
  • Severe hypertension – systolic pressure ≥ 160 mmHg or diastolic pressure ≥ 110 mmHg.

If pre-eclampsia, severe pre-eclampsia, or HELLP or eclampsia, manage as medical emergency.

  • Seek obstetric advice immediately.
  • Unless otherwise advised, give antihypertensive for acute lowering of blood pressure, aiming for blood pressure ≤ 140/100.
  • If severe pre-eclampsia and advised to do so by obstetrician, consider giving magnesium sulphate if available to prevent a primary seizure. Seek obstetric advice.
  • Request acute obstetric assessment and send the patient in by ambulance.​

Clinical guidelines and resources

Diagnosis and treatment of hypertension and pre-eclampsia in pregnancy in NZ – a clinical practice guideline Ministry of Health, NZ, 2018
Drugs and lactation database (LactMed)(external link) US National Library of Medicine
The SOMANZ guideline for the management of hypertensive disorders of pregnancy(external link) Society of Obstetric Medicine of Australia and NZ (SOMANZ), 2014
Hypertension in pregnancy(external link) National Institute for Health and Care Excellence (NICE), UK, 2013

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Reviewed by: Dr Jeremy Tuohy, The University of Auckland

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