10.6 - Disorders of Pregnancy & Parturition: Pre-Eclampsia Flashcards
How common is pre-eclampsia in USA and Europe?
2-4%
How common is pre-eclampsia in Africa and Asia?
8-16%
What is the precise underlying cause of pre-eclampsia?
We don’t know
How do we diagnose pre-eclampsia?
- new onset hypertension (in a previously normotensive woman) - BP >140mmHg systolic and/or >90mmHg diastolic (occurring after 20 weeks gestation)
- reduced foetal movement and/or amniotic fluid volume (by ultrasound) in 30% cases
- oedema common but not discriminatory for PE
- headache (in 40% of severe PE patients)
- abdominal pain (in 15% of severe PE patients)
- visual disturbances, seizures and breathlessness associated with severe PE and risk of eclampsia (seizures)
What is early onset pre-eclampsia?
- one of the subtypes of PE
- <34 weeks
- associated with foetal and maternal symptoms
- changes in placental structure
What is late onset pre-eclampsia?
- one of the subtypes of PE
- > 34 weeks
- more common (90%)
- mostly maternal symptoms
- foetus generally OK
- less overt/no placental changes
What maternal risk factors predispose to pre-eclampsia?
- previous pregnancy with PE
- BMI >30 (especially >35)
- family history
- increased maternal age (>40, <20?)
- gestational hypertension or previous hypertension
- pre-existing conditions: diabetes, PCOS, renal disease, subfertility, autoimmune disease
- non-natural cycle IVF
What risks do pre-eclampsia pose to the mother?
- damage to kidneys, liver, brain and other organ systems
- possible progression to eclampsia (seizures, loss of consciousness)
What risks do pre-eclampsia pose to the foetus?
- reduced foetal growth
- preterm birth
- pregnancy loss/stillbirth
What risk does pre-eclampsia pose to the placenta?
Placental abruption (separation of the placenta from the endometrium)
What happens normally in placental development?
- EVT cell invasion of maternal spiral arteries leads to endothelial and smooth muscle breakdown
- EVT becomes endothelial EVT
- spiral arteries become high capacity
How does placental development change in PE?
- EVT invasion of maternal spiral arteries is limited to decidual layer
- spiral arteries are not extensively remodelled, thus placental perfusion is restricted
What is PLGF?
- placental growth factor
- VEGF related
- pro-angiogenic factor released in large amounts by the placenta
What is Flt1?
- soluble VEGFR1
- soluble receptor for VEGF-like factors which binds soluble angiogenic factors to limit their bioavailability
What happens to Flt1 in pre-eclampsia?
Excess production of Flt-1 by distressed placenta leads to reduction of available pro-angiogenic factors like PLGF and VEGF in maternal circulation, resulting in endothelial dysfunction
How are Flt1 and PLGF levels in healthy placenta?
- releases PLGF and VEGF into the maternal circulation
- these growth factors bind receptors on the endothelial surface to promote vasodilation, anti-coagulation and ‘healthy’ maternal endothelial cells
How are Flt1 and PLGF levels in pre-eclampsia placenta?
- releases sFlT1, which acts as a sponge
- mops up PLGF and VEGF and stops them binding to the endothelial surface receptors
- in the absence of these signals, the endothelial cells become dysfunctional
How are PLGF levels used to predict onset of pre-eclampsia?
- e.g. Triage test
- rules out PE in next 14 days in women 20-36 weeks and 6 days
- PLGF <12pg/ml = positive test, highly abnormal = increased risk for preterm delivery
- PLGF 12<x<100pg/ml = positive test, abnormal = increased risk for preterm delivery
- PLGF >100pg/ml = negative test, normal = unlikely to progress to delivery within 14 days of test
How is sFlt1/PLGF ratio used to predict onset of pre-eclampsia?
- 24-36 weeks plus 6 days gestation
- sFlt1/PLGF <38 = rule out pre-eclampsia
- sFlt1/PLGF >38 = increased risk of pre-eclampsia
What is the only way pre-eclampsia can be resolved?
- by delivery of the placenta
- if <34 weeks, preferable to try and maintain pregnancy if possible for benefit of the foetus
- if >37 weeks, delivery preferable
- in between - case by case basis
How is pre-eclampsia managed?
- anti-hypertensive therapies
- corticosteroids for <34 weeks to promote foetal lung development before delivery
What are the three main ways of preventing pre-eclampsia?
- weight loss (especially if BMI>35)
- exercise throughout pregnancy (seems to work independent of BMI)
- low-dose aspirin (from 11-14 weeks) for high-risk groups - but may only prevent early onset
What are the long term impacts of pre-eclampsia on maternal health?
- elevated risk of cardiovascular disease, T2DM and renal disease after PE
- roughly 1/8 risk of having PE in next pregnancy - greater if early onset
