Pre-eclampsia is a complication of pregnancy characterised by hypertension and proteinuria with or without oedema.
It is a systemic disease whose exact aetiology is still not fully understood, though uteroplacental dysfunction and widespread maternal endothelial dysfunction is seen. It is a significant cause of maternal morbidity and mortality.
Severe cases may result in seizures (eclampsia), multi-organ failure (in particular the liver and kidneys) and significant coagulopathy.
There are a number of terms to be aware of which may be variably defined. Here we present the definitions from the International Society for the Study of Hypertension in Pregnancy (ISSHP), The classification, diagnosis and management of the hypertensive disorders of pregnancy: A revised statement from the ISSHP, 2014.
It can be challenging to make a diagnosis of pre-eclampsia in the setting of pre-existing hypertension or gestational hypertension. Pre-existing renal disease from proteinuria may also add layers of complexity. These patients need close specialist monitoring to identify any signs of pre-eclampsia.
According to NICE CKS, pre-eclampsia affects around 1.5-7.7% of pregnancies.
These figures vary depending upon parity. Around 4.1% of women will experience pre-eclampsia in their first pregnancy compared with 1.7% in their second.
The MBBRACE-UK is a national audit that reviews causes of maternal deaths. Their figures show four deaths per 100,000 pregnancies between 2016-2018 from pre-eclampsia and eclampsia, numbers that reflect a significant fall over the past 50 years.
The exact aetiology and contributing factors can be difficult to assess and attribute, for example in the 2015-17 report they note that of nine women who died of aortic dissection, five were hypertensive and two had pre-eclampsia.
NICE risk stratify certain women as high risk to help guide preventative management.
NICE NG 133: Hypertension in pregnancy: diagnosis and management (2019), describe high risk and moderate risk factors that can be used to guide preventative therapy (see chapter below). Women are considered high risk if they have one of the following high-risk factors:
Women are considered high risk if they have two of the following moderate risk factors:
Studies have also indicated higher incidence in those with African and Caribbean heritage.
Women with one high risk or two moderate risk factors should be offered aspirin prophylaxis.
NICE advise the use of Aspirin 75mg-150mg once daily from 12 weeks until birth in at-risk women to reduce the chance of developing pre-eclampsia.
Standard lifestyle and exercise advice for pregnancy should be given. Ensure modifiable risk factors are addressed and diabetes managed as per guidance.
Pregnant women should be advised to present urgently to hospital if they develop features consistent with pre-eclampsia.
Pre-eclampsia is frequently asymptomatic, picked up during routine antenatal screening based on raised blood pressure and protein in the urine. In more severe disease symptoms may develop including headaches, visual disturbances and abdominal pain.
Onset is after 34 weeks in around 85% of patients. The development of pre-eclampsia before 34 weeks is considered 'early onset'. Pre-eclampsia occurring before 20 weeks is rare and may be associated with a molar pregnancy or antiphospholipid syndrome.
The diagnosis of pre-eclampsia is made by the combination of hypertension (after 20 weeks) and proteinuria.
NOTE: Do not use first morning void to quantify proteinuria.
Placenta growth factor-based tests may be used between 20 and 34+6 weeks gestation, particularly in patients with pre-existing chronic hypertension or gestational hypertension, to help rule in or rule out pre-eclampsia.
The care of any women with pre-eclampsia should be lead by a senior obstetrician.
Optimal management of patients with pre-eclampsia may demand input from multiple teams apart from the obstetricians and can include haematology, intensive care/anaesthetics and neonatology.
The only ‘cure’ is delivery though if patients are stable and closely monitored this can be delayed until 37 weeks. NICE guideline 133 gives an overview of the management of pre-eclampsia.
Where possible, in the absence of severe pre-eclampsia, patients should be managed conservatively until 37 weeks. NICE guideline 133 recommend early birth (i.e. < 37 weeks) should be considered in the following instances (not an exhaustive list):
The thresholds for early birth should be discussed with the mother and decisions about timings advised by consultant obstetricians.
Seizures represent the onset of eclampsia. This is an obstetric emergency requiring an immediate response, commencement of oxygen and securing of the airway. The mother should be placed in the left lateral position. Magnesium sulphate is the first-line treatment for eclamptic seizures. Intubation may be required and cerebral imaging considered. Delivery is the definitive management.
Numerous complications can occur during pre-eclampsia including HELLP syndrome and DIC.
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