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What is Pre-Eclampsia?

Last updated on 28th April 2023

According to the pregnancy charity Tommy’s, pre-eclampsia affects as many as 6% of pregnant women in the United Kingdom. Between 1% and 2% of pregnancies in the UK are affected by severe pre-eclampsia. This condition is also the reason for up to 10% of preterm births. In this article, we’ll discuss what pre-eclampsia is and what to look out for.

What is pre-eclampsia?

Pre-eclampsia is a pregnancy complication. It is also known as toxaemia. When women develop this condition, they have high blood pressure and their urine will contain high amounts of protein, which indicates kidney damage. There might be other signs of damage to organs too.

The condition usually starts after the pregnancy reaches 20 weeks. Left untreated, it can lead to complications – many of them serious and some of them fatal – for both mother and baby.

Obstetricians often recommend delivering the baby early. The timing of this will depend upon the severity of the condition and how many weeks into the pregnancy the patient is.

Before the baby is delivered, pre-eclampsia is treated through medications to lower the blood pressure. Both mother and baby will be carefully monitored too.

Who is most at risk of developing pre-eclampsia?

There are things that increase a woman’s risk of developing the condition.

These include:

  • Having high blood pressure, diabetes, or kidney disease before pregnancy.
  • Having an autoimmune disease like lupus.
  • Having previously had pre-eclampsia or high blood pressure during a past pregnancy.
  • Having a close relative who had pre-eclampsia.
  • Being over 40.
  • A multiple pregnancy.
  • Having a BMI (body mass index) over 35.
Pre-eclampsia risk factors

What are the signs and symptoms of pre-eclampsia?

Most early signs of pre-eclampsia will be picked up by a midwife during routine antenatal appointments. This is because your blood pressure and urine are checked each time.

Pre-eclampsia signs and symptoms in the early stages

As previously mentioned, the initial symptoms of pre-eclampsia are high blood pressure and proteinuria (protein in the urine). However, alone, these symptoms might not mean pre-eclampsia. If they’re found together, it’s usually a strong indicator of pre-eclampsia.

Further symptoms

Aside from these, symptoms of pre-eclampsia include:

  • Severe headaches.
  • Problems with vision like flashing or blurring.
  • Pain below the ribcage.
  • Swelling of the hands, face, or feet that comes on suddenly.
  • Vomiting.

Patients who experience these symptoms should call their midwife or GP urgently. These symptoms are usually seen when pre-eclampsia has progressed.

If pre-eclampsia goes untreated, it can lead to complications.

Signs in the baby

When pre-eclampsia is present, the main sign in the baby is slower growth. This is due to the blood supply being poor as it goes through the placenta. This means that the unborn baby will receive fewer nutrients and less oxygen, which affects how it develops. The medical term for this is foetal growth restriction or intra-uterine growth restriction.

Restricted growth would usually be picked up by a midwife in routine antenatal appointments when measurements of the fundal height are taken.

What causes pre-eclampsia?

There has been no exact cause found for pre-eclampsia but it is believed to happen when the placenta isn’t adequately developed.

The placenta is the vital organ that develops alongside the baby and links the blood supply in the mother to the blood supply in the baby. The baby receives both oxygen and food via this blood supply and its waste products pass back through it into the mother.

To support the unborn baby, the placenta needs a constant and large blood supply from the mother. In pre-eclampsia, it’s believed that the placenta isn’t getting enough blood and the supply is disrupted. Because of this, substances or signals from the placenta affect the blood vessels in the mother and cause hypertension (high blood pressure).

As well as this, kidney problems cause proteins from the mother’s blood to end up in the urine, which causes the proteinuria that is detected in the urine samples.

What causes problems with the placenta?

After the egg is fertilised, it implants itself into the uterus wall. It then anchors itself into the lining with villi – essentially, root-like growths. The blood vessels feed nutrients through these villi and they eventually develop to be the placenta. During the process, the blood vessels become wider and change shape. If they don’t get wide enough, the placenta doesn’t develop as well as it should, which may lead to the mother developing pre-eclampsia.

It isn’t understood why these blood vessels don’t develop as they should, but as it’s quite common to run in families, there could be a genetic cause. Anyone who is considered to be at high risk may be advised to take a dose of 75mg to 150mg of aspirin each day from 12 weeks gestation until the birth. There is evidence to suggest this could lower the chances of developing pre-eclampsia.

What are the complications of pre-eclampsia?

Although pre-eclampsia complications aren’t common, if the condition isn’t diagnosed or monitored, there can be serious problems that affect both the unborn baby and the mother.

Signs and symptoms of pre-eclampsia

Problems affecting the mother

Eclampsia (fits)

Eclampsia itself is actually a type of fit or convulsion. It can happen from 20 weeks until after the birth of the baby (usually within 48 hours of the birth). It rarely occurs before 20 weeks.

Eclampsia is rare. During an eclamptic convulsion, the mother’s legs, arms, jaw or neck will twitch with repetitive, involuntary movements.

During an eclamptic fit, the mother might wet herself and lose consciousness. The fits typically last under one minute.

Most women do make a full recovery after having the condition but there is a very small risk of brain damage or permanent disability if the convulsions are severe.

Sometimes, magnesium sulphate is prescribed to reduce the eclampsia risk.

HELLP syndrome

This is a rare blood clotting and liver disorder that is most likely to occur after birth.

The acronym stands for:

  • H – Haemolysis – the red blood cells break down.
  • EL – elevated liver enzymes (proteins) – when there are high levels of enzymes, it is a sign of damage in the liver.
  • LP – low platelets – platelets are in your blood and are used for clotting.

HELLP syndrome is just as dangerous as eclampsia, but it is more common. The only treatment for this is to deliver the baby.


When a person has high blood pressure, it can disturb the blood supply to the brain, resulting in a cerebral haemorrhage, otherwise known as a stroke. If during this haemorrhage the brain doesn’t get enough nutrients and oxygen from the blood, brain cells die. This results in brain damage, and even death.

Organ problems

There can be other problems to the organs due to pre-eclampsia.

These include:

  • Pulmonary oedema – a fluid build-up around the lungs and in the lungs themselves. This stops the lungs from absorbing enough oxygen.
  • Kidney failure – when a person’s kidneys can’t filter waste products properly from the blood, fluids and toxins build up.
  • Liver failure – pre-eclampsia can cause a disruption to liver function. The liver has lots of different functions, including producing bile, removing toxins, and digesting proteins. Liver damage can be fatal.

Blood clotting disorders

With pre-eclampsia, the blood clotting system can malfunction, which is a condition called disseminated intravascular coagulation.

With a blood clotting disorder, there can be too much bleeding due to an inadequate number of proteins in the blood, or there can be blood clots that develop due to a problem with the proteins that control blood clotting.

The presence of blood clots is problematic because they can block blood flow and also damage organs.

Problems affecting the unborn baby

When mothers have pre-eclampsia during pregnancy, their babies often grow more slowly than usual. This is due to the reduced amount of oxygen and nutrients passing to the baby from the mother.

As a result, babies born to mothers are usually smaller than average, especially if the pre-eclampsia signs began before 37 weeks of gestation.

In severe cases of pre-eclampsia, babies are often delivered before they are fully developed. This in itself can cause complications like breathing difficulties in the baby. Sometimes, the baby might need to spend time in the NICU (neonatal intensive care unit) to be treated and monitored. Very rarely, babies are stillborn as a result of pre-eclampsia.

How is pre-eclampsia diagnosed?

When you’re pregnant, you have frequent appointments with a midwife. At each appointment, you have your vitals checked. This includes your blood pressure, urine, and later on in the pregnancy, the measurement of your fundal height.

It’s also important to be aware of the other pre-eclampsia signs and contact your GP or midwife for advice.

Blood pressure checks

Your blood pressure is checked at each visit. It is measured in mmHg, which means millimetres of mercury. It is a measure of the force exerted on the artery walls (blood vessels) by the blood as it flows.

There are two measures taken:

  • Systolic pressure – this is the pressure when your heart beats and squeezes the blood out.
  • Diastolic pressure – this is the pressure when your heart is at rest between beats.

Your blood pressure is measured with an inflatable cuff on your arm. This has a pressure gauge attached (called a sphygmomanometer). The systolic measurement is the first one taken, followed by the diastolic measurement.

You will often see blood pressure written as 120/80, with the first figure being the systolic blood pressure in mmHg and the second being the diastolic blood pressure in mmHg.

To be considered as high blood pressure in pregnancy, the systolic reading will be 140mmHg and above and the diastolic reading will be 90mmHg and above.

Diagnosing pre-eclampsia

Urine checks

At every antenatal appointment, the pregnant woman is required to provide a urine sample. The urine is tested with a dipstick. The dipstick has been treated with chemicals that react to protein by changing their colour. If there is protein present, the midwife will probably ask for a further sample to be sent to a laboratory.

Blood tests

When the pregnant woman is between 20 and 35 weeks pregnant, there is usually a blood test. If pre-eclampsia is suspected, they will look for PIGF levels. PIGF stands for placental growth factor and it’s a protein. If levels are high, the woman probably doesn’t have pre-eclampsia. If the levels are low, further tests will be needed.

If you’re between 20 weeks and 35 weeks pregnant and your doctors think you may have pre-eclampsia, they may offer you a blood test to help rule out pre-eclampsia.

How is pre-eclampsia treated?

The only way to cure pre-eclampsia is by delivery of the baby. This is because it is due to a problem with the development of the placenta.

When a patient has pre-eclampsia, they will be monitored closely until it is safe to deliver the baby. After diagnosis, the woman is referred to a specialist. A lot of the time, the woman can go home and keep coming back for tests – sometimes even daily. In severe cases, the woman might be admitted to hospital for constant monitoring.

Monitoring in hospital

If hospital monitoring is required, the mother and baby will have lots of checks.

These will include:

  • Regular checks of the blood pressure to assess increases.
  • Regular urine checks to measure levels of protein.
  • Regular blood tests to check liver and kidney health.
  • Ultrasound scans to check placenta blood flow and to measure the amniotic fluid and the baby.
  • Cardiotocography – electronic monitoring of the baby’s heart rate to detect distress or stress.

High blood pressure medication

Medication might be prescribed to lower blood pressure and reduce the risks of serious complications like stroke. In the UK, typical medication might be nifedipine, labetalol and methyldopa. Labetalol is the only one to have been tested on pregnant women in clinical trials and, as a result, is licensed for this purpose. The other two medications, though not licensed for use in pregnancy, can still be used if the benefits will outweigh the risks.

Other medicines

If a woman has severe pre-eclampsia, she might be prescribed anticonvulsant medication to prevent convulsions.

Treating pre-eclampsia

Delivering your baby

For most women with pre-eclampsia, it is recommended that the baby is delivered in week 37 or 38 of pregnancy. This is likely to mean that an induction or caesarean section is required.

With an earlier delivery, you can also reduce the risks of pre-eclampsia complications. In severe cases, it might even be necessary to consider delivering the baby before 37 weeks gestation.

After delivery

Though pre-eclampsia signs usually disappear with the birth of the baby, it is possible to have complications a couple of days afterwards. For this reason, most women who have had pre-eclampsia are required to stay in hospital for monitoring.

If a mother has had a pretty tough time during pregnancy and the birth hasn’t gone as expected, she will have closer monitoring. This is because she might be more at risk of developing postnatal depression or postpartum psychosis.

How to prevent pre-eclampsia?

In some cases, there is nothing you can do to prevent pre-eclampsia. However, those at high risk are often advised to take aspirin from 12 weeks until the birth. Another thing you can do to ensure the best outcome for all is to have a healthy lifestyle during pregnancy.

This includes:

  • Not adding salt to meals.
  • Drinking between 6 and 8 glasses of water every day.
  • Avoiding junk food and fried foods.
  • Getting enough rest.
  • Doing regular exercise.
  • Not drinking alcohol (this is advised against anyway as it can cause serious harm to the unborn child, including foetal alcohol syndrome).
  • Not drinking drinks with caffeine.

Final thoughts on, what is pre-eclampsia?

Pre-eclampsia in pregnancy is largely unavoidable and the cause of it isn’t very well understood. Essentially, the placenta doesn’t work as it should, which causes an excess of protein to be in the urine alongside high blood pressure.

Because pre-eclampsia can lead to severe complications like convulsions, stroke and even death, midwives monitor pregnant women regularly. When pre-eclampsia signs are evident, a woman will have further testing and monitoring. In severe cases, the baby might be delivered early.

For more information, the NICE guidelines cover everything from assessing proteinuria, to managing hypertension and pre-eclampsia, treatment and follow-up in community care. Action on Pre-eclampsia (APEC) also has lots of useful information.

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About the author

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Louise Woffindin

Louise is a writer and translator from Sheffield. Before turning to writing, she worked as a secondary school language teacher. Outside of work, she is a keen runner and also enjoys reading and walking her dog Chaos.

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