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Page last reviewed: 13/07/2011

Pre-eclampsia is a condition that can occur in pregnant women when there is a problem with the placenta (the organ that links the baby's blood supply to the mother's). As a result, the mother can develop:

  • high blood pressure (hypertension)
  • protein in her urine (proteinuria)
  • fluid retention (oedema)

In the unborn baby, pre-eclampsia can cause growth problems (intrauterine growth retardation).

Pre-eclampsia usually occurs during the second half of pregnancy (from around week 20), or immediately after the delivery of a baby. Pre-eclampsia may not be noticeable to the woman who has it, but it will show up during routine antenatal appointments.

In most cases, the symptoms will be monitored with regular blood pressure and urine tests. But some women will need to be admitted to hospital. The only way to prevent pre-eclampsia is to induce labour (start labour artificially) and deliver the baby.

Whether this can be done will depend on how far along the pregnancy is. Being born prematurely (before the 37th week of pregnancy) can be dangerous for the baby, but this may sometimes be necessary to relieve the mother's symptoms.

How common is pre-eclampsia?

Mild pre-eclampsia can affect up to 10% of first-time pregnancies. More severe pre-eclampsia can affect 1-2% of pregnancies. If you have pre-eclampsia during your first pregnancy, you will be more likely to have it again in subsequent pregnancies.

While certain factors have been identified that increase the likelihood of pre-eclampsia, such as having a family history of the condition, the cause of pre-eclampsia is still not fully understood.


Mild pre-eclampsia can be monitored and usually disappears soon after the birth. However, in some cases, further complications can develop, such as eclampsia. This is a type of seizure that the mother can have. It is rare, but can be life threatening for the mother and the baby.

The complications of pre-eclampsia are responsible for the deaths of around six women every year in the UK. Several hundred babies also die each year following complications from severe pre-eclampsia, often as a result of premature birth. Therefore, the earlier that pre-eclampsia is diagnosed and monitored, the better the outlook for mother and baby. 

Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.
High blood pressure
High blood pressure, or hypertension, is when the pressure of the blood in your bloodstream is regularly above 140/90 mmHG.
Kidneys are a pair of bean-shaped organs located at the back of the abdomen. They remove waste and extra fluid from the blood and pass them out of the body as urine.

Page last reviewed: 13/07/2011

Pre-eclampsia cannot happen until you are at least 20 weeks pregnant. Most cases occur in the third trimester (from week 27 to the birth of the baby).

If you notice any symptoms of pre-eclampsia, seek medical advice immediately by calling your GP.

Early symptoms

The initial symptoms of pre-eclampsia are:

  • high blood pressure (hypertension)
  • proteinuria (protein in your urine)

It is unlikely that you will notice either of these symptoms, but your GP or midwife should check for them at your regular antenatal appointments.

Hypertension affects 10-15% of all pregnancies, so this alone does not suggest pre-eclamspia. However, the presence of protein in your urine is a good indicator of the condition.

Progressive symptoms

As pre-eclampsia develops, it can cause fluid retention (oedema). This can cause sudden swelling of your feet, ankles, face and hands.

Oedema is another common symptom of pregnancy, but it tends to be in the lower parts of your body, such as your feet and ankles. It will gradually build up during the day. If the swelling is sudden and, it particularly affects your face and hands, it could be a symptom of pre-eclampsia.

As the condition progresses, your may also have one or more of the following symptoms:

  • severe headaches
  • vision problems, such as blurring or seeing flashing lights before your eyes
  • pain in your upper abdomen (just below your ribs)
  • vomiting
  • excessive weight gain due to fluid retention
  • feeling generally unwell

Seek immediate medical advice if any of these symptoms develop. Without immediate treatment, your condition may deteriorate or you may develop complications.

Symptoms in the unborn baby

The main sign of pre-eclampsia in your unborn baby is slower growth compared to a baby that is developing normally. This is caused by the poor blood supply through the placenta to your baby. Your baby receives less oxygen and nutrients than they should, which can affect their development. This is called intra-uterine growth restriction, or intra-uterine growth retardation.


If it is not diagnosed, pre-eclampsia can cause a number of serious complications, including:

  • eclampsia (convulsions)
  • HELLP syndrome (a combined liver and blood clotting disorder)

See pre-eclampsia - complications for more details about these and other conditions that can result from pre-eclampsia. 

Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart. 
A coma is a sleep like state when someone is unconscious for a long period of time.
Enzymes are proteins that speed-up and control chemical reactions, such as digestion, in the body.
High blood pressure
Hypertension is when the pressure of the blood in your bloodstream is regularly above 140/90 mmHG.
Kidneys are a pair of bean-shaped organs located at the back of the abdomen, which remove waste and extra fluid from the blood and pass them out of the body as urine.
The liver is the largest organ in the body. Its main jobs are to secrete bile (to help digestion), detoxify the blood and change food into energy.
Lungs are a pair of organs in the chest that control breathing. They remove carbon dioxide from the blood and replace it with oxygen.
Pain is an unpleasant physical or emotional feeling that your body produces as a warning sign that it has been damaged.
Platelets are cells in the blood that control bleeding by plugging the broken blood vessel and helping the blood to clot.
Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.
Vomiting is when you bring up the contents of your stomach through your mouth.

Page last reviewed: 13/07/2011

The cause of pre-eclampsia is not fully understood. However, it is thought that a problem may develop with the blood vessels in the placenta, resulting in its underdevelopment.

The placenta

The placenta is the organ that links your blood supply to your unborn baby's blood supply. Food and oxygen passes through the placenta from your blood into the baby. Waste products can pass from the baby back into you.

In order to support your growing baby, the placenta needs a large and constant supply of blood from you. In pre-eclampsia, the placenta does not get enough blood. This could be due to a problem with the placenta's development as it was forming, during the first half of your pregnancy.

A problem with the placenta

In the initial stages of pregnancy, the fertilised egg implants itself into the wall of the uterus (womb). The uterus is a female hollow, pear-shaped organ in which a baby grows during pregnancy. The egg produces root-like outgrowths called villi, which help to anchor it to the lining of the uterus.

The villi are fed nutrients through spiral-shaped arteries in the uterus. The villi will eventually grow into the placenta. Some ideas about what causes pre-eclampsia are based on these spiral-shaped arteries in the uterus, and the important role they play in the development of the placenta.

During the early stages of pregnancy, these spiral arteries are remodelled (they change shape) and become wider. If the arteries do not fully transform, it is likely that the placenta will not develop properly because it will not get enough nutrients. This may then lead to pre-eclampsia.

It is still unclear why the spiral arteries do not transform as they should. Some research has suggested a possible link between pre-eclampsia, miscarriage and infertility. It is possible that the same medical reasons that cause infertility and miscarriage are responsible for the problems that lead to pre-eclampsia.

However, the exact nature of pre-eclampsia and why it affects certain people, is still being researched.

Disrupted blood flow

The problem with the placenta means that the blood supply between you and your baby is disrupted. Signals from the damaged placenta affect your blood vessels, causing hypertension (high blood pressure). The signals also disturb your kidney function.

Waste products that should be removed from your blood and passed out in your urine, remain in the blood. At the same time, valuable proteins that should remain in your blood are leaked into your urine, causing proteinuria (protein in your urine).

Influencing factors

Some factors have been identified that could increase your chance of developing pre-eclampsia. These are listed below.

  • If it is your first pregnancy, pre-eclampsia it is more likely than during any subsequent pregnancies.
  • If you have had a child, but it has been at least 10 years since your last pregnancy, your risk of developing pre-eclampsia is slightly higher.
  • If you have a family history of the condition - for example, your mother or sisters have had pre-eclampsia, your chances of developing the condition increases.
  • If you have had pre-eclampsia in a previous pregnancy, there is approximately a 20% chance that you will develop the condition again in later pregnancies.
  • Your age influences the likelihood of developing pre-eclampsia; if you are a teenager, or over 40 years old, you have a higher chance of developing it.
  • If you have an existing medical problem - for example, diabetes, kidney disease, migraines or high blood pressure, you are more at risk of getting pre-eclampsia.
  • If you are obese at the start of your pregnancy, pre-eclampsia is more likely. Obesity is defined as having a body mass index (BMI) of 30 or more.
  • If you are expecting multiple babies, such as twins or triplets, pre-eclampsia is more likely because there is more strain on the placenta.
Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.
Blood vessels
Blood vessels are the tubes in which blood travels to and from parts of the body. The three main types of blood vessels are veins, arteries and capillaries.
Genetic is a term that refers to genes- the characteristics inherited from a family member.
High blood pressure
Hypertension is when the pressure of the blood in your bloodstream is regularly above 140/90 mmHG.
Kidneys are a pair of bean-shaped organs located at the back of the abdomen, which remove waste and extra fluid from the blood and pass them out of the body as urine.

Page last reviewed: 13/07/2011

Pre-eclampsia is diagnosed when hypertension (high blood pressure) is combined with proteinuria (protein in your urine). Both of these tests are carried out as a standard part of your antenatal appointments with your GP or midwife.

At your first antenatal appointment, your GP or midwife will discuss any factors that may increase your chance of developing pre-eclampsia. If you are identified as having an increased risk - for example, you have had pre-eclampsia in an earlier pregnancy, your blood pressure may be monitored more closely.

In many cases, you will not notice that you have pre-eclampsia. Only your GP or midwife will pick up on it. However, if you begin to notice symptoms, contact your GP for advice.

Blood pressure

Your blood pressure will be monitored throughout your pregnancy at regular antenatal screenings. It is taken using two measurements. The first measurement is known as systolic, which is the pressure in your arteries when your heart contracts and pushes the blood around your body. The second measurement is known as diastolic, which is the pressure in your arteries when your heart refills with blood in between heart beats. Both systolic and diastolic blood pressures are measured in millimetres of mercury (mmHg).

Your GP or midwife will use a sphygmomanometer to measure your blood pressure (a device with an inflatable cuff and a scale of mercury as a pressure gauge). You will be given your systolic reading first, followed by your diastolic reading. If your systolic blood pressure is 120 mmHg and your diastolic blood pressure is 80 mmHg, you will be told that your blood pressure is 120 over 80, which is commonly written as 120/80.

See the low blood pressure Health A-Z topic for a more detailed explanation about how your blood pressure is measured.

Hypertension during pregnancy is usually defined as a systolic reading of 140 mmHg or more, or a diastolic reading of 90 mmHg or more. Severe hypertension is a systolic reading of 160 mmHg or more, or a diastolic reading of 110 mmHg or more.

Urine tests

A urine sample is usually asked for at every antenatal appointment. You should use a sterile container to collect a sample of urine a few seconds after you first start to pass urine. Take this with you to your appointment.

The urine sample can easily be tested for protein using a dipstick. This is a strip of paper that has been treated with chemicals so that it reacts to the presence of protein, usually by changing colour.

If the dipstick is positive for protein, your GP or midwife may ask for another urine sample to send to a laboratory for further tests. This could be a single sample of urine, or you may be asked to provide several samples of urine over a 24-hour period. These can be used to determine exactly how much protein is being lost through your urine. If you have 0.3g of protein in your urine over a 24-hour period, it is usually a sign of pre-eclampsia.

Further tests

You will have more frequent antenatal appointments if you have either hypertension or proteinuria. If your symptoms are severe, or get worse, you may be admitted to hospital for closer observation (see pre-eclampsia - treatment).

Page last reviewed: 13/07/2011

Pre-eclampsia can only be prevented by delivering your baby. Treatment tends to focus on closer monitoring and trying to lower your blood pressure until delivery of the baby is possible.

If your GP or midwife identifies the symptoms of pre-eclampsia, you will be referred for further tests. Depending on the severity of your symptoms, this could be another appointment with them in a week's time, a referral to a hospital within 48 hours, or a referral to a hospital on the same day.

Further tests will determine the severity of your pre-eclampsia, and whether you need to go to hospital.

Mild pre-eclampsia

Mild pre-eclampsia will be monitored with more frequent antenatal appointments. At these appointments:

  • your blood pressure will be checked for any increase (hypertension)
  • your urine will be tested for protein (proteinuria)
  • you will be asked about any other symptoms that you have.

Depending on other symptoms or influencing factors, if you are between 24 and 32 weeks into your pregnancy, you will be asked to attend an antenatal appointment at least every three weeks. If you are beyond 32 weeks into your pregnancy, this will be every two weeks. 

There are recommendations for healthcare professionals to use when treating pre-eclampsia. These include:

  • giving you information about the condition based on the current evidence, including the signs and symptoms of pre-eclampsia, how it may develop, and how serious your case is
  • providing support to enable you to make informed decisions about your care
  • arranging a medical review with you after any abnormal blood tests, so that you can discuss the results and be given a summary of your assessment
  • arranging a new antenatal care plan with you, including a follow-up appointment
  • allocating a consultant (a specialist doctor) to you
  • providing a way for you to report and act on any new symptoms - for example, a direct number to call
  • arranging a convenient way to inform you of any future test results

The care that you receive will be a specific program designed for you, depending on what services are available in your area and what your symptoms require. You should discuss any concerns about your antenatal plan with your GP or midwife.  

Severe pre-eclampsia

If your pre-eclampsia is severe, you may need to be admitted to hospital for closer monitoring and treatment. As pre-eclampsia tends to get worse rather than better, it is unlikely that you will be able to go home until after your baby is born. 


You and your unborn baby will be monitored in the following ways:

  • your blood pressure will be checked every 4-6 hours for any abnormal increases
  • urine samples will be taken at least every 24 hours to measure your protein levels
  • you will be asked about any other symptoms you are having
  • your blood may be tested for aspartate aminotransferase (AST) and alanine aminotransferase (ALT). These are enzymes (proteins that speed-up and control chemical reactions); if found in the blood they can be a sign of liver damage
  • a full blood count may be taken from a sample of your blood to provide information about your red and white blood cells and your platelets
  • ultrasound scans (sonographs) - high frequency sound waves are used to create an image of the baby; they will check the blood flow through your placenta, measure the size of the foetus, and observe your baby's breathing and movements
  • the growth rate of the baby will be closely monitored to check for intrauterine growth retardation (IUGR) - i.e. a slow rate of growth
  • your baby's heart rate may be monitored electronically in a process called cardiotocography. This keeps a close watch on your baby's immediate wellbeing, as it can detect any distress in the baby.


Treatment focuses on the symptoms of pre-eclampsia, particularly high blood pressure. Bed rest and antihypertensive medication (such as calcium channel blockers) can be used to lower your blood pressure. This will reduce the likelihood of complications caused by high blood pressure, such as strokes (when the blood supply to the brain is disturbed).

You may also be prescribed anticonvulsant medication to prevent the convulsions (fits) of eclampsia. Injections of magnesium sulphate can halve the risk of pregnant women developing eclampsia. They can also be used to treat convulsions if they occur. 

Premature birth

The only cure for pre-eclampsia is to deliver your baby and remove the placenta as soon as possible. A baby that is born before the 37th week of pregnancy is premature and may not be fully developed. However, if your baby is seriously affected by pre-eclampsia, or there is a strong risk of further complications, it may be necessary to deliver your baby prematurely.  

Attempts will be made to manage your pre-eclampsia until a delivery after 36 weeks of pregnancy. Some recent research has suggested that once the baby reaches 37 weeks, it may be better to induce labour (start labour artificially), rather than wait and carefully monitor the baby until it is born naturally. This reduces the risk of complications from pre-eclampsia, including HELLP syndrome and eclampsia.

The premature delivery of your baby will usually be done by caesarean section (through an incision in your abdomen). You should be given information about the risks of both premature birth and pre-eclampsia, so that the best decision for your treatment can be made.

Anticonvulsant medicine is used to treat epilepsy and seizures. For example Lorazepam.
Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.

Page last reviewed: 13/07/2011

If pre-eclampsia is not diagnosed and monitored, a number of serious complications can develop. These are listed below.


Eclampsia is a term that describes a type of convulsion (involuntary contraction of the muscles) that pregnant women can experience, usually from week 20 of the pregnancy, or immediately after the birth. Eclampsia is quite rare - for example, a 2005 survey found that there are about three cases of eclampsia for every 10,000 births.

During an eclamptic convulsion, your arms, legs, neck or jaw will twitch involuntarily in repetitive, jerky movements. You may lose consciousness and you may wet yourself. The convulsions usually last less than a minute.

While most women make a full recovery after having eclampsia, there is a small risk of permanent disability or brain damage if the convulsions are severe. Around 1 in 50 women will die from the condition. Unborn babies can suffocate during a seizure, and 1 in 14 may die.

Research has found that magnesium sulphate can halve the risk of eclampsia and reduce the risk of the mother dying. It is now widely used to treat eclampsia after it has occurred, and to treat women who may be at risk of developing it.

HELLP syndrome

HELLP syndrome is a combined liver and blood clotting disorder that can affect pregnant women. It is most likely to occur immediately after the baby is delivered, but can appear any time after week 20 of the pregnancy.

The name, HELLP, stands for each part of the condition:

  • H - haemolysis - the red blood cells in your blood break down
  • EL - elevated liver enzymes - enzymes are proteins that speed up and control chemical reactions in the body; a high level in the liver is a sign of liver damage
  • LP - a low platelet count - platelets are cells in the blood that help it to clot.

HELLP syndrome is potentially as dangerous as eclampsia, and it is slightly more common. The only way to treat the condition is to deliver the baby as soon as possible. Once the mother is in hospital and is receiving treatment, it is possible for her to make a full recovery. The main danger to the baby is from premature birth (being born before the 37th week of pregnancy).

Premature babies often have a low birth weight and find it hard to breathe on their own. It is likely that they will need to stay in neonatal intensive care for close supervision. If the baby's birth weight less than 1,500 g (3½ lbs), the baby has a 1 in 6 chance of dying before their first birthday.

Cerebral haemorrhage

A cerebral haemorrhage, more commonly known as a stroke, is where the blood supply to your brain is disturbed. If your brain does not get enough oxygen and nutrients from your blood, your brain cells will start to die.

Pulmonary oedema

Pulmonary oedema is where fluid builds up in and around your lungs. This stops them from working properly by preventing them from absorbing oxygen.

Kidney failure

If your kidneys cannot filter waste products from your blood, toxins and fluids build up in your body. Your blood will not function normally because it is not being cleaned properly.

Liver damage

Your liver has many functions, including digesting proteins and fats, producing bile, and removing toxins. Any damage that disrupts these functions could be fatal. 

Disseminated intravascular coagulation

Disseminated intravascular coagulation is where your blood clotting system breaks down, and the proteins that control blood clotting become abnormally active.

Page last reviewed: 13/07/2011

Your recovery

For most women, delivery of the baby reverses all the effects of pre-eclampsia. There is still a possibility of developing eclampsia soon after the birth, but this is rare. There is also a slight risk of organ damage if you had complications during the pre-eclampsia.

If you have had pre-eclampsia in past pregnancies, you are more likely to have it again in subsequent pregnancies. Make sure that you inform your GP or midwife at any future antenatal appointments, as they may want to monitor you more closely.

Your baby's recovery

Pre-eclampsia should not have any long-term effects on your baby, unless your baby was extremely starved of oxygen in the womb, or born very prematurely. If so, your baby may not be fully developed when they are born.

Your baby might need to stay in a neonatal intensive care unit. This can replicate the functions of the womb and allow your baby to fully develop. Once it is safe to do so, you will be allowed to take your baby home.

Page last reviewed: 13/07/2011

Attending all of your antenatal appointments is the most important thing that you can do to prevent pre-eclampsia.

If your GP or midwife finds that you have hypertension (high blood pressure) or proteinuria (protein in your urine), you should take an active interest. Make sure that you are given a referral or a follow-up appointment. If you notice any symptoms yourself, report them to your GP.

There are currently no standard recommendations to prevent pre-eclampsia, but some research suggests that taking the following steps might help:

  • increase your intake of the antioxidants contained in vitamin C, vitamin E, selenium, and lycopene, although these may also increase the risk of premature birth
  • increasing the calcium in your diet
  • some evidence suggests that resting for at least four hours a day may help if you are at high risk of developing pre-eclampsia
  • low-dose aspirin may reduce the risk of pre-eclampsia if you are at high risk, but it should not be taken without your GP's advice.

The following have been shown to have no benefit in cutting the risk of developing pre-eclampsia:

  • losing weight during pregnancy, even if you are obese and subsequently at greater risk of developing pre-eclampsia
  • restricting salt in your diet
  • increasing the amount of energy in your diet - for example, with energy or protein supplements
  • taking fish oil supplements
  • taking evening primrose oil

Predicting pre-eclampsia

It is not possible to predict when pre-eclampsia will occur, or how severe it will be. Some research has investigated whether blood pressure readings taken in the earlier stages of pregnancy are a good indicator of the future development of pre-eclampsia. It found only mixed results. The mean arterial pressure (a measurement calculated from your standard blood pressure reading) was slightly more useful.

Other research has investigated whether increased amounts of proteinuria are linked to worse outcomes for the mother and the baby. For example, whether more protein in the mother's urine leads to a higher risk of mortality (death) for either the mother or the baby, or whether the baby is more likely to be admitted to a neonatal intensive care. However, no such links were found.

Given the uncertainty surrounding the development of pre-eclampsia, it is even more important that you attend all of your antenatal appointments.

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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