Pre-eclampsia and Eclampsia
Pre-eclampsia occurs only during pregnancy (generally after 20 weeks) and during the period immediately after the birth. It can affect both mother and unborn baby. It is a complication of 2-3 percent of all pregnancies and 5-7 per cent of first pregnancies and is a major cause of growth restriction in the uterus and perinatal mortality. Pre-eclampsia is also a major reason for delivering babies prematurely.
A small proportion of women with pre-eciampsia (2 per cent) go on to develop convulsions, known as eclampsia. Risk factors for pre-eclampsia include:
- A first pregnancy
- Being pregnant with twins or triplets
- A new partner
- Previous pre-eclampsia or a family history of pre-eclampsia (for example, a sister or mother)
- A pre-existing medical problem, for example, high blood pressure or diabetes.
Although the exact causes of pre-eclampsia are not fully understood, current understanding suggests that the placenta is mainly responsible. Failure of the fertilized egg to implant properly in the uterus results in the placenta receiving less blood from the mother's uterine arteries. This triggers a sequence of events that can harm the mother, especially her cardiovascular, urinary and central nervous systems and her liver. It also affects her blood-clotting mechanism, can adversely affect the growth of the fetus and increases the risk of placental abruption.
Symptoms and diagnosis
Early symptoms of pre-eclampsia include visual disturbance (such as flashing lights), headache, upper abdominal pain, vomiting and rapidly worsening swelling (for example, of the legs and ankles). However, most women do not complain of any symptoms when the condition first arises, so diagnosis depends on the vigilance of the midwife or doctor. Therefore, pre-eclampsia is more commonly diagnosed when classic signs of high blood pressure, high levels of protein in the urine (proteinuria) and swelling appear. Pre-eclampsia is an enigmatic condition that presents itself in a great variety of ways, so it is not always easy to spot. Blood tests are also useful in diagnosis.
Eclampsia is diagnosed when convulsions (fits) occur alongside symptoms of pre-eclampsia. Of these seizures, 44 per cent occur postnatally, 38 per cent before birth and 18 per cent during birth.
All pregnant women should have their blood pressure monitored regularly and their urine tested. Women who are at particular risk of developing pre-eclampsia should be given extra tests, for example, blood tests to check kidney and liver function, and blood counts. Ultrasound scanning of the uterine artery (by Doppler measurements) can detect abnormalities in blood flow at 20-24 weeks. Women with a decreased blood flow are at greater risk of developing disease.
The only cure for pre-eclampsia is delivery of the fetus and placenta. However, for women with only mild disease, the plan is usually to continue the pregnancy until it is safe to deliver the baby. On the other hand, if the condition is severe or life-threatening, which unfortunately can occur very early in pregnancy, there may be only a few hours in which to act. Treatment therefore depends on the severity of the disease and the how long the baby has been developing.
Biood pressure treatment is sometimes advisable, either in the longer term in mild disease (for example, with oral medication such as methyldopa or a beta blocker) or in the short term (often with intravenous drugs), as part of an intensive treatment regime aimed at stabilizing the mother's condition before delivery. In severe cases, intravenous magnesium sulphate is commonly used in order to orevent eclampsia occurring.
Low doses of aspirin (75 mg/day) - or calcium, vitamins C and E and folic acid - may help to prevent pre-eciampsia in women who are particularly at risk.