Pre-eclampsia

Definition

Definition and diagnostic criteria

• Pre-eclampsia is defined by a new onset of blood pressure of ≥ 140/90 mmHg after 20+0 weeks.

Classification

Types and risk factors

• Early-onset pre-eclampsia (before 34+0 weeks) is typically placental with growth restriction.
• The single strongest risk factor for developing pre-eclampsia is history of pre-eclampsia.
• Other major risk factors include chronic hypertension, kidney disease, diabetes mellitus, and autoimmune diseases (SLE, APS).

Pre-eclampsia and superimposed pre-eclampsia

• Pre-eclampsia is present when gestational hypertension is accompanied by proteinuria or at least one other maternal organ manifestation or uteroplacental dysfunction.
• The former classification into 'mild' and 'severe' pre-eclampsia has been abandoned; instead, today the organ manifestations are named.
• If pre-eclampsia develops on the basis of pre-existing hypertension, it is called superimposed pre-eclampsia.

Special forms and diagnostics

• HELLP syndrome and eclampsia are considered severe manifestation and not separate primary categories.

Aetiopathogenesis

Impaired placentation

• The two-stage model begins with an incomplete invasion of the trophoblast into the spiral arteries.
• Consequently, the physiological remodelling into wide, low-resistance vessels incomplete.
• The consequence of this first stage is placental malperfusion with oxidative stress, which initiates the second stage of the disease.

Anti-angiogenesis and endothelial damage

• The ischaemic placenta releases increased levels of anti-angiogenic factors, primarily sFlt-1 (soluble fms-like tyrosine kinase-1) and endoglin.
• sFlt-1 leads to a deficiency of free pro-angiogenic factors by binding and inactivating PlGF and VEGF.
• The clinical result is a generalised endothelial dysfunction with hypertension, oedema and proteinuria.

Clinical features

Clinical organ involvement

• Liver involvement presents with right-sided or epigastric upper abdominal pain, as well as transaminases that are are more than double the normal limit.
• Haematological signs include thrombocytopenia with counts < 100,000/µl, haemolysis, or disseminated intravascular coagulation.
• Neurological symptoms include new-onset headaches, visual disturbances such as flashing scotomas, or hyperreflexia and clonus.
• A uteroplacental manifestation can present as growth restriction/abnormal Doppler.

More facts from the study questions

• In the absence of proteinuria, a single other new-onset organ manifestation is sufficient for diagnosis.
• The diagnostic criteria require hypertension plus either proteinuria or other organ involvement.
• A history of pre-eclampsia in a previous pregnancy is the strongest single risk factor.
• Other risk factors include chronic hypertension, diabetes mellitus and autoimmune diseases.
• The threshold for relevant thrombocytopenia in pre-eclampsia is a count below 100,000 per µl.
• Counts between 100,000 and 150,000 per µl are low but do not define the haematological criterion.
• Liver involvement can present with right upper quadrant or epigastric pain.
• A rise in transaminases to more than double the normal value is a diagnostic criterion.
• The definition of severe hypertension in pregnancy is blood pressure values of 160/110 mmHg or higher.
• If a patient with pre-existing chronic hypertension newly develops the criteria for pre-eclampsia, this is termed superimposed pre-eclampsia.

Diagnosis

Diagnostic correlates

• A sonographic correlate of the impaired invasion in the first stage is an increased PI and notch in uterine arteries.
• The key laboratory correlate of the second stage is the elevated sFlt-1/PlGF ratio.
• A low sFlt-1/PlGF ratio rules out pre-eclampsia short-term.

History and clinical examination

• In addition to standardised blood pressure measurement and lung auscultation, the clinical examination includes assessing the reflex status with clonus testing.
• A rapid increase in oedema and weight is also an important important warning sign.

Laboratory and urine tests

• Urinalysis includes a dipstick test and measurement of the protein-to-creatinine ratio.
• The so-called HELLP panel includes a full blood count and specifically haptoglobin, LDH, as well as transaminases (AST, ALT).
• A specific marker for risk stratification is the serum sFlt-1/PlGF ratio.

Typical imaging findings

• Ultrasound: The waveform rises steeply and then falls, producing a clear incisure immediately after systole; only then does diastolic flow continue at a low level. The pattern repeats identically with every heartbeat.

Keep learning in the app

Further reading (selection)

1. StatPearls: Preeclampsia (NCBI Bookshelf)
2. WHO fact sheet: Pre-eclampsia
3. DocCheck Flexikon, Präeklampsie
4. DocCheck Flexikon, Schwangerschaftsinduzierte Hypertonie

Cross-references