Description

While significant anaemia is unusual in term newborns, anaemia is the most frequent haematological abnormality in premature infants. The two most common causes are physiological anaemia of prematurity and blood loss due to repeated blood sampling. Anaemia of prematurity results in a lower Hb nadir (6.5-9g/dl) compared to term babies (10-11g/dl) and it occurs earlier (4-8 weeks). It is often, unlike the physiological anaemia in term babies, a true anaemia since oxygen delivery is diminished. The pathogenesis is multifactorial: red cell lifespan is shortened, the oxygen affinity of HbF is high compared with HbA; the demand for increasing red cell mass due to growth leads to haematinic deficiency unless supplemented; there are large phlebotomy losses due to frequent laboratory monitoring; and there is a state of relative erythropoietin deficiency. Interestingly, recent data are suggestive of real differences in cytokine production and responsiveness between neonatal and adult haemopoietic cells which may also contribute to anaemia of prematurity.