Toxaemia of pregnancy (pre-eclampsia)
Pre-eclampsia is a condition that can affect pregnant women, resulting in high blood pressure and damage to one or more organs, often the kidneys (causing protein in the urine).
Pre-eclampsia affects about 15,000 pregnant women in Australia every year. It is usually diagnosed after 20 weeks of pregnancy, most often in the third trimester. In some women pre-eclampsia occurs soon after giving birth to their baby, although this is much less common.
Pre-eclampsia can lead to serious complications for mother and baby, so early detection and treatment are essential.
Signs and symptoms of pre-eclampsia
Pre-eclampsia, which occurs only in pregnancy, has several features. Two common signs of pre-eclampsia are:
- high blood pressure; and
- the appearance of protein in the urine.
Because these signs often don’t cause any symptoms, they are usually detected at a routine ante-natal check-up.
Other features of pre-eclampsia may include:
- oedema (swelling), usually of the face, hands, feet and ankles;
- persistent headaches;
- blurred vision;
- shortness of breath;
- nausea and vomiting; and
- upper abdominal pain.
If you are pregnant and develop a severe or persistent headache, abdominal pain or sudden onset of blurred vision, you should seek urgent medical attention.
Early detection and treatment are important in pre-eclampsia.
Most women who have had a baby will remember having their blood pressure checked frequently during the pregnancy. These blood pressure checks, along with regular urine tests, are part of routine ante-natal (before birth) care of mothers and babies. Although these visits to the doctor or clinic may seem a nuisance to pregnant mothers who are feeling perfectly well, they are very important, especially in the later stages of the pregnancy.
Because raised blood pressure and protein in the urine are the most common signs of early pre-eclampsia, all pregnant women are routinely checked for these signs, which often don’t cause any symptoms.
Pre-eclampsia can also involve the liver, blood clotting, nervous system and the developing baby.
While the exact cause of pre-eclampsia is not known, it is thought to be related to a problem with the placenta — the connection between mother and baby. The placenta provides oxygen and nutrients to your developing baby.
In pre-eclampsia, the blood vessels that supply the placenta don’t develop properly, leading to problems with the placenta itself. This may affect blood flow through the placenta and also affect the mother’s blood pressure.
It’s possible that the immune system or certain genes are involved in the development of pre-eclampsia.
Several factors are known to increase the risk of developing pre-eclampsia.
The main risk factors include:
- having had pre-eclampsia in a previous pregnancy; or
- having pre-existing high blood pressure, diabetes, kidney disease, clotting disorders or lupus.
Additional factors that can increase your risk (particularly if there are 2 or more risk factors) include:
- if it is your first pregnancy, or your first pregnancy with your current partner;
- having a family history of pre-eclampsia;
- being older than 40 years of age;
- being obese;
- being pregnant with more than one baby (e.g. twins); and
- having a gap of more than 10 years between pregnancies.
There are complications associated with pre-eclampsia, some of which are serious. Close monitoring and treatment aim to prevent these serious complications from developing.
Complications that can affect the mother include:
- HELLP syndrome. This complication can develop in women with severe pre-eclampsia, and involves damage to the liver leading to elevated liver enzymes, problems with blood clotting and damage to red blood cells. HELLP syndrome can be life-threatening.
- Eclampsia is when seizures (fits) occur in women with pre-eclampsia. This is a serious but rare complication in Australian women.
- Stroke, which can result from very high blood pressure.
The baby can also be affected. A poorly functioning placenta, with inadequate blood supply, is not good for the developing baby, which may not grow as well as it should before birth. This is known as fetal growth restriction.
Tests and Diagnosis
In many cases, pre-eclampsia is first diagnosed after routine blood pressure checks and/or urine tests reveal abnormalities.
Your doctor will ask about any symptoms you have that are suggestive of pre-eclampsia.
Your doctor will also perform a physical examination, including a blood pressure check and check on your baby.
If pre-eclampsia is suspected, further assessment and testing may be recommended in hospital or a day assessment unit under the care of an obstetrician (specialist in pregnancy and childbirth).
Tests may include:
- urine tests for protein;
- blood tests to check your kidney function, liver enzymes and platelets (cells in the blood that are responsible for clotting); and
- ultrasound scans to check the baby’s development, the amount of amniotic fluid and blood flow through the umbilical artery to the baby.
Treatment for pre-eclampsia
Treatment will depend on the severity of the pre-eclampsia and the stage of pregnancy.
Monitoring and treatment before delivery
Women diagnosed with pre-eclampsia before 37 weeks of pregnancy can often be treated with medicines and careful monitoring of their condition and the unborn baby. Monitoring and treatment in hospital is necessary for many women.
Women with pre-eclampsia need to have their blood pressure closely monitored and treated if necessary. There are several medicines used to treat high blood pressure (anti-hypertensives) that are considered safe to use in pregnancy.
Medicines such as magnesium sulfate can also be given to treat or prevent eclampsia (seizures).
The only ‘cure’ for pre-eclampsia is for the baby to be born.
If you have pre-eclampsia, your doctor will usually recommend that you deliver your baby at about 37 weeks of pregnancy to reduce the risk of complications. Delivery may be an induced labour or Caesarean section.
Sometimes the baby will need to be delivered before 37 weeks (premature birth). This is recommended when the pre-eclampsia is a risk to the mother or baby. When it is necessary to deliver the baby prematurely, corticosteroid medicines are often given to the mother before the birth to help mature the baby’s lungs before delivery.
Ongoing monitoring and treatment is needed after the baby is born, as high blood pressure can continue for several weeks.
There is some evidence to suggest that taking low-dose aspirin during pregnancy can reduce the risk of developing pre-eclampsia. Low-dose aspirin may be recommended for women who are at increased risk of developing pre-eclampsia.
Calcium supplements have also been found to reduce the risk of pre-eclampsia in women who are at risk of pre-eclampsia, especially if their calcium intake is low.
Always check with your doctor before taking any medicines or supplements during pregnancy.
Long-term effects of pre-eclampsia
Studies have shown that having had pre-eclampsia can increase a woman’s risk of developing high blood pressure, heart disease and stroke later in life.
Ensuring that you follow a healthy lifestyle (not smoking, maintaining a healthy weight, eating a healthy diet and getting regular physical activity) can help lower your risk of cardiovascular disease.
Your doctor may also recommend yearly blood pressure checks, as well as regular cholesterol and diabetes checks.
Support is available for those affected by pre-eclampsia. Talk to your doctor, who can refer you to a support group such as Australian Action on Pre-eclampsia (AAPEC). Some women and their partners may benefit from counselling.
Last Reviewed: 05/08/2016
Your Doctor. Dr Michael Jones, Medical Editor.
1. Society of Obstetric Medicine of Australia and New Zealand (SOMANZ). Guideline for the management of hypertensive disorders of pregnancy, 2014. https://somanz.org/downloads/HTguidelineupdatedJune2015.pdf (accessed Aug 2016).
2. Mayo Clinic. Preeclampsia (updated 3 Jul 2014). http://www.mayoclinic.org/diseases-conditions/preeclampsia/basics/definition/con-20031644 (accessed Aug 2016).
3. NHS Choices. Pre-eclampsia (updated 2 Jun 2015). http://www.nhs.uk/conditions/Pre-eclampsia/Pages/Introduction.aspx (accessed Aug 2016).
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