Persistent fetal circulation is a condition caused by a failure in the systemic circulation and pulmonary circulation to convert from the antenatal circulation pattern to the "normal" pattern.
In a fetus, there is high pulmonary vascular resistance and low pulmonary blood flow as the fetus does not use the lungs for oxygen transfer. Once the baby is born, the lungs are needed for oxygen transfer and need high blood flow which is encouraged by low pulmonary vascular resistance.
It can be associated with pulmonary hypertension. Because of this, the condition is also known as "persistent pulmonary hypertension of the newborn".
It occurs in 1-2 infants per 1000 live births
Normal vascular anatomy with functional vasoconstriction 
This has a good prognosis, as it is reversible. Causes include hypoxia, meconium aspiration, and respiratory distress syndrome.
Decreased diameter of pulmonary vessels with hypertrophy of vessel walls 
This has a poor prognosis, as it is a fixed abnormality. Causes include post-term pregnancy, placental insufficiency, and NSAID use by the mother.
Decreased size of pulmonary vascular bed 
This has a poor prognosis, as it is a fixed abnormality. It is caused by space occupying lesions such as pleural effusions and diaphragmatic hernias.
Functional obstruction of pulmonary blood flow 
This has a good prognosis if it is reversible. Causes include polycythemia and hyperfibrinogenemia. 
Treatment aims to increase the amount of oxygen in the blood and reverse any causes of hypoxia.
- oxygen therapy
- mechanical ventilation
- NO Inhalation
- Prostaglandins (intravenous)
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