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Fetal haemoglobin left shift — FRCA Primary MCQ

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HardPhysiologyFetal haemoglobin left shiftFRCA Primary

A neonate undergoing pyloromyotomy has haemoglobin F predominance. Compared with adult haemoglobin, what is the most relevant effect for oxygen carriage?

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Correct answer: D — Higher oxygen affinity from reduced 2,3-DPG binding

Fetal haemoglobin binds 2,3-DPG less avidly, shifting the dissociation curve left and increasing oxygen affinity. This facilitates placental oxygen uptake but may reduce tissue unloading compared with adult haemoglobin. It does not inherently reduce arterial oxygen content at the same haemoglobin concentration. Neonatal oxygen physiology differs materially from adult physiology.

Reference: West Respiratory Physiology; Ganong Review of Medical Physiology