Pre-eclampsia & Eclampsia are hypertensive disorders of pregnancy, which may lead to significant maternal and foetal morbidity and mortality, with increased resistance in the uterine arteries on Doppler ultrasound.
Description
Pre-eclampsia is a disorder of pregnancy characterised by new-onset hypertension and proteinuria after the 20th week of gestation. It is considered one of the leading causes of maternal and perinatal morbidity and mortality worldwide. Eclampsia is the progression of pre-eclampsia to seizures, which are not attributed to other causes.
Pathogenesis
The pathogenesis of pre-eclampsia and eclampsia involves multiple factors and remains incompletely understood. However, it is thought to involve abnormal placental development, systemic inflammation, endothelial dysfunction, and an imbalance in angiogenic and anti-angiogenic factors.
In the early stages of normal pregnancy, there is a process known as remodelling of the spiral arteries, in which trophoblast cells invade the uterine spiral arteries and transform these small, high-resistance vessels into large, low-resistance vessels. This ensures adequate blood flow to the developing foetus.
In pre-eclampsia, this process is believed to be defective. The inadequate remodelling of the spiral arteries leads to poor placental perfusion and subsequent hypoxia. This is thought to result in the release of inflammatory cytokines and anti-angiogenic factors into the maternal circulation, leading to systemic inflammation, endothelial dysfunction, and the clinical features of pre-eclampsia.
The progression to eclampsia, where seizures occur, is thought to be due to severe hypertension leading to cerebral oedema and disruption of the blood-brain barrier. However, the exact pathophysiology remains unclear.
Epidemiology, Risk Factors & Associations
- Pre-eclampsia occurs in 2-8% of all pregnancies.
- Risk factors include nulliparity, maternal age >40 years, obesity, multiple gestation, history of pre-eclampsia, and pre-existing conditions such as chronic hypertension and renal disease.
- Eclampsia is typically associated with severe pre-eclampsia but can occur even in mild cases or without any preceding signs of pre-eclampsia.
Clinical Features
- Hypertension and proteinuria are the hallmark features of pre-eclampsia.
- Other features include oedema, headaches, visual disturbances, and right upper quadrant or epigastric pain.
- In eclampsia, seizures occur, which are not attributable to other causes.
Complications
- Maternal complications include progression to eclampsia, HELLP syndrome (Haemolysis, Elevated Liver enzymes, Low Platelet count), and increased risk of cardiovascular disease later in life.
- Foetal complications include intrauterine growth restriction, preterm birth, and perinatal death.
Pathological Features
Histopathology
- Macroscopic: The placenta in pre-eclampsia may be small and pale with infarcts.
- Microscopic: Features include fibrinoid necrosis, atherosis of spiral arteries, and increased syncytial knots in the placenta.
Serology
- Elevated levels of liver enzymes
- Decreased platelet count.
Biochemistry
- Proteinuria is a key biochemical finding.
Radiological Features
General Features
- Doppler ultrasound shows increased resistance in the uterine arteries.
Ultrasound
- B-mode: The placenta may appear echogenic due to infarcts. There may be associated intrauterine growth restriction in the foetus.
- Colour Doppler: Shows increased resistance and notch sign in the uterine arteries.
Diagnosis
The diagnosis of pre-eclampsia is made based on the clinical features of hypertension and proteinuria after the 20th week of gestation. Eclampsia is diagnosed when seizures occur in a woman with pre-eclampsia.
Differential Diagnosis
- Chronic hypertension: Typically presents prior to 20 weeks of gestation and lacks associated proteinuria.
- Gestational hypertension: Occurs after the 20th week of gestation, but no proteinuria.
Management
Management of pre-eclampsia involves close monitoring of maternal and foetal well-being, blood pressure control, and timely delivery of the foetus. Management should be in a multidisciplinary setting involving obstetricians, neonatologists, and anaesthesiologists. Eclampsia is a medical emergency requiring stabilisation of the mother, control of seizures, and expedited delivery.