Pre-eclampsia
How the placenta normally remodels the mother’s spiral arteries into wide, low-resistance channels, why failed remodelling leaves it starved of blood, and how factors from the stressed placenta damage the mother’s blood vessels, kidneys, liver and brain.
By the end, you can
- Describe normal placentation and spiral artery remodelling.
- Explain how shallow trophoblast invasion leads to placental ischaemia.
- Explain how anti-angiogenic factors cause widespread maternal endothelial dysfunction.
- Relate hypertension, proteinuria, headache, visual change, abdominal pain and low platelets to organ involvement.
- Describe eclampsia, HELLP syndrome and fetal growth restriction, and why delivery of the placenta resolves the disease.
- Recognise the diagnostic thresholds, severe features, HELLP criteria and classic placental, kidney and liver appearances, and explain how aspirin, antihypertensives, magnesium sulfate and delivery act on the mechanism.
What it is
Pre-eclampsia is new high blood pressure after 20 weeks of pregnancy with protein in the urine or other signs of organ dysfunction (kidney, liver, brain, blood or placental). It begins with a poorly perfused placenta and causes widespread injury to the mother’s endothelium. It affects a few percent of pregnancies and resolves after the placenta is delivered.
3 types to tell apart
- Early onset
- Before 34 weeks; strongly linked to abnormal placentation and fetal growth restriction; usually more severe.
- Late onset
- From 34 weeks; more often linked to maternal factors and a large or ageing placenta.
- With severe features
- Very high blood pressure, eclampsia, HELLP, kidney or liver injury, pulmonary oedema or visual and neurological symptoms.
Normal function
Wide channels to the placenta
In early pregnancy, trophoblast cells from the placenta invade the uterine lining () and the inner {{myometrium}}. They replace the muscle and elastic tissue of the mother’s , converting them into wide, floppy channels that no longer constrict.
This remodelling delivers a large, steady, low-pressure flow of maternal blood into the , where it bathes the villi and exchanges oxygen and nutrients with fetal blood without mixing.
Across the mother’s body, pregnancy normally widens blood vessels: plasma volume and cardiac output rise, and blood pressure falls slightly in mid-pregnancy. The placenta releases growth factors such as PlGF that support healthy endothelium.
| Feature | Normal | Pre-eclampsia |
|---|---|---|
| Trophoblast invasion | Deep, into inner myometrium | Shallow, decidua only |
| Artery wall | Muscle replaced; wide and floppy | Muscular; narrow and reactive |
| Flow into placenta | Large, steady, low pressure | Fast, pulsatile, intermittent jets |
| Placenta | Well perfused | Ischaemic, oxidative stress |
Underlying change · Step 1 of 4
Shallow invasion, narrow arteries
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 2 of 4
Signals from a stressed placenta
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 3 of 4
Organs of mother and baby
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Consequences · Step 4 of 4
Emergencies and the cure
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Symptoms and signs
Symptoms, signs and findings
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Exam detail
Exam detail
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Treatment
How treatment works
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Recap
Recap
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Self-check
Check your understanding
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .