Pre-eclampsia is a complication of pregnancy. Women with pre-eclampsia have high blood pressure (hypertension), protein in their urine and may develop other symptoms and problems. The more severe pre-eclampsia is, the greater the risk of serious complications to both mother and baby. The exact cause of pre-eclampsia is uncertain but it is thought to be due to a problem with the afterbirth (placenta). The only way to cure pre-eclampsia is by giving birth to (delivering) your baby. Medication may be advised to help prevent complications of pre-eclampsia.
What are pre-eclampsia and eclampsia?
Pre-eclampsia is a condition that only occurs during pregnancy. It causes high blood pressure (hypertension) and it also causes protein to leak from your kidneys into your urine. This can be detected by testing your urine for protein. Other symptoms may also develop (see below). Pre-eclampsia usually comes on sometime after the 20th week of your pregnancy and gets better within six weeks of you giving birth. The severity can vary. Pre-eclampsia can cause complications for you as the mother, for your baby, or for both of you (see below). The more severe the condition becomes, the greater the risk that complications will develop. Around 1 in 200 pregnant women in the UK develop pre-eclampsia.
Eclampsia is a type of fit (a seizure or convulsion) which is a life-threatening complication of pregnancy. Less than 1 in 100 women with pre-eclampsia develop eclampsia. So, most women with pre-eclampsia do not go on to have eclampsia. However, treatment and care of women with pre-eclampsia is mainly to prevent eclampsia and other possible complications.
Is pre-eclampsia the same as gestational high blood pressure?
No. Many pregnant women develop mild high blood pressure (hypertension) that is not pre-eclampsia. This is known as gestational high blood pressure or pregnancy-induced high blood pressure.
Gestational high blood pressure is high blood pressure that comes on for the first time ever after the 20th week of pregnancy. Doctors can confirm this type of high blood pressure if you do not go on to develop pre-eclampsia during your pregnancy and if your blood pressure has returned to normal within six weeks of you giving birth. If you have gestational high blood pressure, you do not have protein in your urine when it is tested by your midwife or doctor during your pregnancy. With pre-eclampsia, you have high blood pressure plus protein in your urine and sometimes other symptoms and complications listed below. See separate leaflet called Pregnancy and High Blood Pressure for more details.
Note: some women may be found to have new high blood pressure after 20 weeks of pregnancy. At first, they may not have any protein in their urine on testing. However, they may later develop protein in their urine and so will then be diagnosed with pre-eclampsia. You are only said to have pregnancy-induced or gestational high blood pressure if you do not go on to develop pre-eclampsia during your pregnancy.
What causes pre-eclampsia and who develops it?
The exact cause is not known. It is probably due to a problem with the afterbirth (placenta). This is the attachment between your baby and your womb (uterus). It is thought that there are problems with the development of the blood vessels of the placenta in pre-eclampsia and also damage to the placenta in some way. This may affect the transfer of oxygen and nutrients to your baby.
Pre-eclampsia can also affect various other parts of your body. It is thought that substances released from your afterbirth go around your body and can damage your blood vessels, making them become leaky.
Any pregnant woman can develop pre-eclampsia. However, there are some women who may be more likely to develop it. Pre-eclampsia also runs in some families, so there may also be some genetic factor.
You have a moderately increased risk of developing pre-eclampsia if:
- This is your first pregnancy, or it has been 10 years or more since your last pregnancy.
- You are aged 40 or more.
- You are obese (your body mass index (BMI) is 35 or over).
- You have a pregnancy with twins, triplets, or more.
- Your mother or sister has had pre-eclampsia.
You have a higher risk of developing pre-eclampsia if:
- You have had high blood pressure (hypertension) or pre-eclampsia during a previous pregnancy.
- You have diabetes or chronic (persistent) kidney disease.
- You had high blood pressure before the pregnancy started.
- You have antiphospholipid syndrome. (Women with this condition have an increased risk of having a miscarriage and also of developing blood clots.)
- You have systemic lupus erythematosus. (This is a condition that can cause various symptoms, the most common being joint pains, skin rashes and tiredness. Problems with kidneys and other organs can occur in severe cases.)
How is pre-eclampsia diagnosed?
Pre-eclampsia is present if:
- Your blood pressure becomes high; and
- You have an abnormal amount of protein in your urine.
High blood pressure (hypertension) means that the pressure of the blood in your blood vessels (arteries) is too high. Blood pressure is recorded as two figures. For example, 140/85 mm Hg. This is said as '140 over 85'. Blood pressure is measured in millimetres of mercury (mm Hg). The first (or top) number is your systolic blood pressure. This is the pressure in your arteries when your heart contracts. The second (or bottom) number is your diastolic blood pressure. This is the pressure in your arteries when your heart rests between each heartbeat.
Normal blood pressure is below 140/90 mm Hg. During pregnancy:
- Mildly high blood pressure is blood pressure between 140/90 and 149/99 mm Hg.
- Moderately high blood pressure is blood pressure between 150/100 and 159/109 mm Hg.
- Severely high blood pressure is blood pressure of 160/110 mm Hg or higher.
Some women with pre-eclampsia develop certain symptoms (see below). These symptoms should alert them to see their doctor or midwife who will check their blood pressure, test their urine for protein and diagnose pre-eclampsia. However, other women, especially those with mild pre-eclampsia, may not know that they have pre-eclampsia. They may not have any symptoms. This is why it is very important to have regular checks of your blood pressure and your urine during pregnancy.
Initially, a simple test can be used to check for protein in your urine. During this test, a special stick called a urine dipstick is used. If you are found to have protein in your urine on testing with a dipstick, your doctor or midwife may suggest that you collect your urine over a 24-hour period so that the total amount of protein in your urine can be measured.
What are the symptoms of pre-eclampsia?
The severity of pre-eclampsia is usually (but not always) related to your blood pressure level. You may have no symptoms at first, if you only have mildly raised blood pressure and a small amount of protein in your urine.
If pre-eclampsia becomes worse, one or more of the following symptoms may develop. See a doctor or midwife urgently if any of these occur:
- Severe headaches that do not go away.
- Problems with your vision, such as blurred vision, flashing lights or spots in front of your eyes.
- Tummy (abdominal) pain. The pain that occurs with pre-eclampsia tends to be mainly in the upper part of your abdomen, just below your ribs, especially on your right side.
- Vomiting later in your pregnancy (not the morning sickness of early pregnancy).
- Sudden swelling or puffiness of your hands, face or feet.
- Not being able to feel your baby move as much.
- Just not feeling right.
Note: swelling or puffiness of your feet, face, or hands (oedema) is common in normal pregnancy. Most women with this symptom do not have pre-eclampsia but it can become worse in pre-eclampsia. Therefore, report any sudden worsening of swelling of the hands, face or feet promptly to your doctor or midwife.
Rarely, pre-eclampsia and eclampsia can both develop for the first time up to four weeks after you have given birth. So, you should still look out for any of the symptoms above after you give birth and report them to your doctor or midwife.
What are the possible complications of pre-eclampsia?
Most women with pre-eclampsia do not develop serious complications. The risk of complications increases the more severe the pre-eclampsia becomes. The risk of complications is reduced if pre-eclampsia is diagnosed early and treated.
For the mother
Serious complications are uncommon but include the following:
- Eclampsia (described above).
- Liver, kidney, and lung problems.
- A blood clotting disorder.
- Bleeding into the brain (a stroke).
- Severe bleeding from the afterbirth (placenta).
- HELLP syndrome. This occurs in about 1 in 5 women who have severe pre-eclampsia. HELLP stands for 'Haemolysis, Elevated Liver enzymes and Low Platelets', which are some of the medical features of this severe form of pre-eclampsia. Haemolysis means that your blood cells start to break down. Elevated liver enzymes means that your liver has become affected. Low platelets means that the number of platelets in your blood is low and you are at risk of serious bleeding problems. The job of platelets is to help your blood to clot.
For the baby
The poor blood supply in the placenta can reduce the amount of food and oxygen reaching the growing baby. On average, babies of mothers with pre-eclampsia tend to be smaller. There is also an increased risk of premature birth and of stillbirth. Babies are also more likely to develop breathing problems after they are born.
What is the treatment for pre-eclampsia?
If you develop pre-eclampsia, you will usually be referred urgently to see a specialist (an obstetrician) for assessment and care. You may be admitted to hospital. If you develop new high blood pressure (hypertension) or new protein in your urine, you will also usually be referred for a specialist opinion.
Tests may be done to check on your well-being and that of your baby; for example, blood tests to check how your liver and kidneys are working. You may also be asked to collect your urine over a 24-hour period so that the amount of protein in your urine can be measured. A recording of your baby's heart rate may be done, as well as an ultrasound scan to see how well your baby is growing and a scan to see how well the blood is circulating from the afterbirth (placenta) to your baby.
Your blood pressure will be checked regularly and your urine will usually be tested at frequent intervals for protein. You should also look out for any symptoms of pre-eclampsia and tell your midwife or doctor if you develop any of these.
Giving birth to your baby
The only complete cure for pre-eclampsia is to give birth to your baby. At delivery, your placenta is delivered just after your baby is born. Therefore, what is thought to be the cause of the condition is removed. After the birth, your blood pressure and any other symptoms usually soon settle.
It is common practice to induce your labour if pre-eclampsia occurs late in your pregnancy. A caesarean section can be done if necessary. The risk to your baby is small if he or she is born just a few weeks early.
However, a difficult decision may have to be made if pre-eclampsia occurs earlier in your pregnancy. The best time to give birth to your baby has to balance several factors which include:
- The severity of your condition, and the risk of complications occurring for you.
- How severely your baby is affected.
- The chance of your baby doing well if they are born prematurely. In general, the later in your pregnancy your baby is born, the better. However, some babies grow very poorly if the afterbirth does not work well in severe pre-eclampsia. They may do much better if they are born, even if they are premature.
As a rule, if pre-eclampsia is severe then delivery sooner rather than later is best. If pre-eclampsia is not too severe then postponing delivery until nearer the full term may be best.
Until your baby is delivered, other treatments that may be considered include:
- Medication to reduce your blood pressure. This may be an option for a while if pre-eclampsia is not too severe. If your blood pressure is reduced it may help to allow your pregnancy to progress further before you give birth to your baby.
- Steroid drugs. These may be advised to help your baby's lungs to mature if doctors feel that there is a chance that they will need to deliver your baby and your baby is still premature.
- Magnesium sulfate. Studies have shown that if mothers with pre-eclampsia are given magnesium sulfate, it roughly halves the risk of them developing eclampsia. Magnesium sulfate is an anticonvulsant (it helps to stop you having a seizure) and it seems to prevent eclampsia much better than other types of anticonvulsants. It is usually given for about 24 hours by a drip (a slow infusion directly into a vein) around the time of delivery.
Can pre-eclampsia be prevented?
There is some evidence to suggest that regular low-dose aspirin and calcium supplements may help to prevent pre-eclampsia in some women who may be at increased risk of developing it.
The National Institute for Health and Care Excellence (NICE) provides guidance and sets quality standards to improve people's health in the UK. NICE has suggested that women at increased risk of developing pre-eclampsia should consider taking low-dose aspirin. If you have at least two of the moderate-risk factors for pre-eclampsia listed above, or at least one of the high-risk factors listed above, NICE suggests that you take low-dose aspirin (a 75 mg tablet every day) from 12 weeks of your pregnancy until the birth of your baby.
One study involving almost 16,000 women found that calcium supplements during pregnancy were a safe way of reducing the risk of pre-eclampsia in women at increased risk. However, previous evidence about calcium supplements in preventing pre-eclampsia has been conflicting and confusing. So, further research is needed regarding calcium supplements and their role in pre-eclampsia prevention, including the ideal dose of calcium supplements to take.
Aspirin or calcium supplements are not standard or routine treatments for all women during pregnancy. However, one or other (or both) may be suggested by a specialist if you have a high risk of developing pre-eclampsia. You should not take either aspirin or calcium supplements unless you have been advised to do so by your specialist. Discuss it with them first.
What is my risk of developing pre-eclampsia again in a future pregnancy?
If you had pre-eclampsia in your first pregnancy:
- You have somewhere between a 1 in 2 and a 1 in 8 chance of developing gestational high blood pressure (gestational hypertension) next time you are pregnant.
- You have about a 1 in 6 chance of developing pre-eclampsia next time you are pregnant.
If you had severe pre-eclampsia, HELLP syndrome or eclampsia that meant that your baby had to be delivered before 34 weeks, you have about a 1 in 4 chance of developing pre-eclampsia next time you are pregnant.
If you had severe pre-eclampsia, HELLP syndrome or eclampsia that meant that your baby had to be delivered before 28 weeks, you have about a 1 in 2 chance of developing pre-eclampsia next time you are pregnant.
Being obese is a risk factor for pre-eclampsia (see above). If you have had pre-eclampsia in a previous pregnancy and you are planning for another pregnancy but you are overweight or obese, you should try to lose weight before you become pregnant again. This may help to reduce your chance of developing pre-eclampsia in your next pregnancy. See separate leaflet called Weight Reduction - How to Lose Weight for more details.
Could pre-eclampsia have any effects on my future health?
Some research has shown that women who develop pre-eclampsia may have a slightly higher chance of developing high blood pressure (hypertension) and have a higher chance of having a heart attack or stroke in the future. However, the overall risk of developing these problems is still low. Therefore, you may wish to look at ways in which you may be able to reduce your risk of these complications by making changes to your lifestyle. These can include keeping to a healthy weight, exercising regularly, eating a healthy, balanced diet and not smoking. See separate leaflet called Preventing Cardiovascular Diseases for more details.
If you have had pre-eclampsia during your pregnancy, it is important that your blood pressure is checked when you leave hospital after you have given birth. This will usually be done by a midwife who visits you at home. Your blood pressure should also be checked at your 6- to 8-week postnatal appointment to make sure that it has returned to normal. Your urine should be checked for protein at this time as well.
Further help & information
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Tel: 020 8427 4217
Further reading & references
- Antenatal care for uncomplicated pregnancies; NICE Clinical Guideline (March 2008, updated 2017)
- Hypertension in pregnancy; NICE Clinical Guideline (August 2010, updated 2011)
- Hypertension in pregnancy; NICE Quality Standard, July 2013
- Hypertension in pregnancy; NICE CKS, April 2015 (UK access only)
- Williams D, Craft N; Pre-eclampsia. BMJ. 2012 Jul 19;345:e4437. doi: 10.1136/bmj.e4437.
- Hofmeyr GJ, Lawrie TA, Atallah AN, et al; Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems. Cochrane Database Syst Rev. 2010 Aug 4;8:CD001059.
Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but makes no warranty as to its accuracy. Consult a doctor or other healthcare professional for diagnosis and treatment of medical conditions. For details see our conditions.
Dr Tim Kenny
Dr Jacqueline Payne
Dr John Cox