LEARNING TOPIC
Preeclampsia and eclampsia

  updated 13 May 1999 

Keywords
  • Eclampsia
  • blood pressure
  • pregnancy
  • convulsions
  • maternal mortality
  • fetal compromise
   

High blood pressure is the most common major medical problem of pregnancy and a leading cause of maternal mortality. In its most severe form there is risks to the mother from multisystem manifestations which may necessitate early delivery. Associated vascular pathology in the placenta and uteroplacental bed may compromise the fetus. The fetus is therefore at risk from placental insufficiency in addition to the risks of premature delivery. High blood pressure occurs in up to 15% of women in their first pregnancy. Many classifications for the disease have been derived. Perhaps the simplest classification is the idea of hypertension in pregnancy being either pregnancy induced or pregnancy aggravated. Pregnancy induced hypertension typically occurs in an otherwise well women with no risk factors. It is truly a problem peculiar to pregnancy. Pregnancy aggravated occurs in pregnancy to a women with an underlying predisposition whether that be essential hypertension, renal disease or other conditions. Definitions for the hypertensive disorders of pregnancy have been developed by the American College of Obstetricians and Gynaecologists.

Hypertension: Systolic blood pressure > 140mmHg; diastolic blood pressure >90 mmHg; or a systolic increase of 30 mmHg, diastolic increase of 15 mmHg.

Proteinuria: Protein levels, >300 mg in 24 hours or > 1g/L on dipstick in at least two random urine specimens, collected 6 or more hours apart.

Preeclampsia: The development of hypertension with proteinuria, edema, or both after 20 weeks` gestation.

Eclampsia: The occurrence of convulsions in a preeclamptic patient in the absence of coincidental neurologic disease.

Chronic hypertension: The presence of persistent hypertension of whatever cause prior to 20 weeks` of gestation in the absence of neoplastic trophoblastic disease.

Superimposed preeclampsia or eclampsia: The development of preeclampsia or eclampsia in a women with pre-existing hypertensive vascular or renal disease.

Gestational hypertension: Hypertension developing in the latter half of pregnancy not accompanied by other evidence of preeclampsia or chronic hypertensive vascular disease.

Severe preeclampsia: Blood pressure >160/110 mmHg proteinuria (>5g in 24 hours) oliguria (<500 ml in 24 hours), rising serum creatinine, persistent visual disturbances, epigastric or right upper quadrant pain, pulmonary edema or right upper quadrant pain, pulmonary edema or cyanosis, thrombocytopenia or overt hemolysis, hepatocellular damage, and intrauterine growth retardation.

Hypertension in pregnancy is an important disease because of maternal complications that may ensue. The commonest reason for maternal death is cerebral haemorrhage. This may be associated with eclampsia and is attributed to focal cerebral ischaemia. Antepartum haemorrhage and placental abruption may occur. Acute renal failure may develop. An intravascular coagulation process localised in the placental bed or disseminated and widespread throughout the mother may be associated with consumption of platelets and clotting factors. In the liver the focal vascular lesions and periportal haemorrhage may be associated with elevated enzymes. Liver swelling and subcapular haemorrhage may occur. It is important to note that until the more serious manifestations occur the mother may feel well. Hence the importance of clinical vigilance and early surveillance of mother in whom a rise in blood pressure is detected.

The hypertension disorders of pregnancy present major risks to the mother and fetus. In general terms the management centres on controlling the disorder in the mother in order to allow the fetus to grow and mature. Delivery is indicated if the process cannot be controlled in the mother or the risks to the fetus of delivery are less than the intrauterine hazards. The definitive treatment is therefore delivery (uterine evacuation).

The correct timing of delivery is a critical part of the management.

Indications for delivery in preeclampsia:

Maternal

  • Inability to control blood pressure
  • Deteriorating liver function
  • Deteriorating renal function
  • Progressive thrombocytopaenia
  • Neurological complications

Fetal

  • Persistent non-reactive fetal heart rate tracing, contraction induced late decelerations.
  • Intrauterine growth restriction, failure of ultrasound growth.

Safeguarding the mother during the time around delivery involves protection from the risks of acute hypertension and convulsion as well as support of renal, hepatic and haematological systems.

The cause of preeclampsia and eclampsia remains uncertain. Genetic factors are important and indeed familial inheritance patterns are described. An excessive placental mass has been implicated as the condition is more common in twins and may occur in association with hydatidiform mole when no fetus is present. Immunological factors are often implicated as the condition is more common in first pregnancy or first pregnancy with a new partner and less likely in women who have experienced a previous miscarriage or received a blood transfusion. The widespread vascular pathology is unified by current thoughts that endothelial cell damage with plays a critical role causing platelet and fibrin deposition. It is possible that this follows trophoblast injury and placental ischaemia. The statement that preeclampsia is a disease of theories is as appropriate today as it was 25 years ago.

Recommended and Optional Readings and Resources

See reading list

Author/s:   Prof. Brian Trudinger, Dept of Obstsetrics and Gynaecology, Westmead Hospital