Haemoglobin is the substance in the blood which carries oxygen (air) around the body and makes the blood look red in colour. Every unborn baby produces a minor adult type haemoglobin called Hemoglobin A2; this haemoglobin is produced irrespective of the type of major adult haemoglobin they have inherited from their parents. Haemoglobin A2 is useful for helping the laboratory to diagnose some genetic mutations of haemoglobin, depending on the type of genetic mutation that has been inherited the level of A2 will rise or fall.