Potter sequence refers to a series of developmental abnormalities resulting from prolonged oligohydramnios (↓ amniotic fluid).
This lack of amniotic fluid causes mechanical compression of the fetus and defective lung development, often leading to fatal pulmonary hypoplasia.
Pathophysiology
| Step | Pathologic Process | Consequence |
|---|---|---|
| 1 | Oligohydramnios (↓ amniotic fluid volume) | Reduced cushioning for the fetus |
| 2 | Fetal compression by the uterine wall | Limb deformities, facial anomalies |
| 3 | Decreased fetal breathing movements and amniotic fluid aspiration | Pulmonary hypoplasia |
| 4 | Respiratory failure after birth | Common cause of neonatal death |
Causes of Oligohydramnios
| Category | Specific Cause | Mechanism |
|---|---|---|
| Renal / Urinary abnormalities | Bilateral renal agenesis | No fetal urine production |
| Autosomal recessive polycystic kidney disease (ARPKD) | Impaired urine output | |
| Obstructive uropathy (e.g., posterior urethral valves) | Urine outflow obstruction | |
| Placental causes | Chronic placental insufficiency | Decreased fetal perfusion and urine output |
| Membrane causes | Preterm premature rupture of membranes (PPROM) | Amniotic fluid leakage |
| Drug-related | Maternal ACE inhibitor or ARB use | Fetal renal failure and ↓ urine production |
Clinical Features
| System | Findings |
|---|---|
| Facial | Flattened nose, low-set ears, micrognathia (retrognathia) |
| Limbs | Club feet, limb deformities due to compression |
| Thorax / Lungs | Pulmonary hypoplasia (↓ alveolar development) |
| Genitourinary | Often associated with renal agenesis or cystic kidneys |
| Outcome | Respiratory insufficiency → death shortly after birth |
Mnemonic: “POTTER” Sequence
| Letter | Meaning |
|---|---|
| P | Pulmonary hypoplasia (cause of death) |
| O | Oligohydramnios (initiating event) |
| T | Twisted face |
| T | Twisted skin |
| E | Extremity deformities |
| R | Renal failure (agenesis, dysplasia, or obstruction) |
Key Points to Remember
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Primary event: Oligohydramnios → fetal compression + pulmonary hypoplasia
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Most common fatal outcome: Respiratory failure from lung hypoplasia
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Common causes: Bilateral renal agenesis, ARPKD, chronic placental insufficiency, ACE inhibitor exposure
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Characteristic features: Flattened facial profile, limb deformities, and underdeveloped lungs
🧠 Learning Objective
By the end of this topic, the student should be able to:
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Explain the pathophysiology of the Potter sequence.
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Identify the characteristic physical features and causes.
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Correlate oligohydramnios with pulmonary hypoplasia and perinatal death.
