Pre-eclampsia is a dangerous complication of pregnancy, which can affect both mother and baby. Dr Howard Lee looks at the causes and treatment

This is a condition that is unique to pregnancy and usually occurs after the 20th week of gestation, although it can occur earlier.

Up to 1 in 10 women suffers from pre-eclampsia, but the severity can vary from 'nothing to worry about' to 'serious concern' about the mother and baby, so a more reassuring statistic shows that only 1 in 100 women is severely affected.

Pregnant women are quite often admitted to the antenatal ward with high blood pressure (hypertension) - and the level of concern at this stage will depend on what is causing the hypertension - and how high the blood pressure is, of course.

Measuring blood pressure levels:

• A blood pressure greater than 140/90 in pregnancy is considered raised.
• Very high blood pressure is greater than 170/110

It does seem that some women develop hypertension only when they are pregnant, but this usually resolves itself after delivery. This is called Pregnancy-Induced Hypertension (PIH).

Hypertension can be one of the signs and symptoms of pre-eclampsia and, unless it is very high, a woman will not be aware that her blood pressure has increased, because she will have no symptoms.

What are the other symptoms and signs of pre-eclampsia?

As well as high blood pressure, pre-eclampsia can cause:

• Protein in the urine (Proteinuria) - because the kidneys have been affected by the disease, and protein 'leaks' away in the urine.
• Sudden or severe swelling (Oedema) affecting feet, hands or even the face. Some swelling in the feet is normal in pregnancy. This usually appears at the end of the day, and settles after a night's bed rest. The swelling of pre-eclampsia is often associated with:
• Excessive weight gain
• Severe headache and/or dizziness
• Visual disturbances - seeing 'spots' or 'flashing lights'
• Pain in the right, upper abdomen - which may indicate liver involvement
• Vomiting late in pregnancy.

Who is at risk?

First time mothers - and those pregnant for the first time by a new partner
• Teenagers and those over 35
• Those with chronic medical problems, which include hypertension, kidney problems, diabetes, and, to a lesser extent, migraine.
• Those of short stature
• Those who are underweight
• Those carrying twins or multiple pregnancies
• Those with a past history of pre-eclampsia, especially if this was severe
• Those with a family history of pre-eclampsia
• Those with a Pregnancy-induced Hypertension (PIH) - see above.

What causes the disease?

We still don't know why certain women develop the disease. Some researchers think that the placenta (after-birth) is at the root of the problem, although it is not known why this affects some pregnant women and not others.

Scientists have detected a chemical in women with pre-eclampsia and, in the future, it may be possible to do an early blood test, well before symptoms occur, to alert doctors to the risk.

Other theories include insufficient blood flow to the uterus, hormone imbalances, immune activation and lack of magnesium, calcium or selenium.

How can you reduce the risk of pre-eclampsia?

Many trials, using different drugs and supplements, have been carried out in an effort to prevent the disease.

• Halibut Liver Oil in one trial has been suggested - but there have been no promising results - and some people are concerned about its use.
• Increase of dietary Proteins has also been suggested - but is not encouraged by other researchers.
• Calcium/Vitamin C & E supplements in early pregnancy have had some early, encouraging results, it seems.
• Low Dose Aspirin has possibly shown a preventative effect, and some think that it certainly has a place - but other research does not support this finding.

Pre-eclampsia cannot be predicted, reliably prevented, or treated

Because pre-eclampsia is known to be associated with serious dysfunction of the placenta, doctors and midwives are concerned about the health of the baby, when it happens.

Ultimately, the only treatment is delivery of the baby, which could, of course, in some cases put the baby at severe risk from 'prematurity'.

If you do develop pre-eclampsia, you will be asked to have more regular checks of both your blood pressure and your urine. You may be encouraged to bed-rest at home or even be admitted to hospital - or referred to the Day Unit of the antenatal department - for further observation and monitoring.

These checks could consist of:

• 4-6 hourly blood pressure measurements
• 24-hour urine collection - in order to measure the amount of protein
• Routine blood samples - in order to determine the severity of the disease
• Ultrasound - to determine your baby's growth and monitor your baby?s heart to watch for signs of distress.

Drugs may be necessary in order to reduce high blood pressure. Remember that I have already mentioned the only real 'cure' for pre-eclampsia is delivery of your baby.

If the pre-eclampsia is very bad, your doctor may want to induce you to start your labour and in some cases a Caesarean Section may be necessary.

The risks of pre-eclampsia

For the baby: While unborn, the supply of oxygen and nutrients can be dangerously reduced because of the damage to the placenta (after birth).

This long-standing damage to the life-line may already have caused some retardation in the baby's growth - which can be seen on the ultrasound scanning.

On the other hand, if delivered prematurely, the chances of survival may be reduced. As far as the baby's health is concerned, the timing of the delivery can involve difficult, and emotionally 'charged' decisions, by the doctors who are involved with the care of the mother and baby.

For the mother: The changes in blood pressure can be life threatening and may have a detrimental effect on her circulation and many of her internal organs.

The frightening figure for the UK, of 7-10 maternal deaths - as a result of untreated pre-eclampsia - and up to 900-1000 deaths of babies each year, as result of severe pre-eclampsia, has to be mentioned.

In severe cases of pre-eclampsia, and where delivery has occurred, the mother will be carefully monitored over several days, as there is a risk of eclampsia itself - a life threatening disease for the mother.

There is some positive news

The majority of mothers with pre-eclampsia do, fortunately, make a good recovery. Their symptoms usually disappear after delivery, and the blood pressure and 'urine protein' return to normal after two weeks or so.

Their babies, too, survive the precarious few weeks, recover and continue to thrive.

These same women often go on to enjoy normal health in a subsequent pregnancy. It is very important, therefore, to attend all your antenatal check-ups so that any pre-eclampsia can be detected early and carefully managed.

Remember, too, that in most cases - even if you have to be admitted to hospital - the bed rest does produce a gradual fall in blood pressure, which is often sufficient to delay the need for premature delivery of the baby.

This in turn, will afford the baby an increased chance of survival.

If you have a history of pre-eclampsia, closer and more frequent health monitoring will be necessary in any subsequent pregnancies. This will start earlier in the pregnancy than usual, or ideally, even before conception.

The message is: consult your doctor and plan ahead.