Iron status of preterm infants after hospital discharge : a thesis presented in partial fulfilment of the requirements for the degree of Masters in Science in Nutrition and Dietetics at Massey University, Albany, New Zealand

Abstract

Background: Preterm infants are at an increased risk of developing iron deficiency (defined in paeditaric populations as a ferritin value <12 μg/L or a serum transferrin receptor concentration >2.4 mg/L) after discharge due to their shortened gestational length, increased requirements for rapid growth, and excessive blood losses through phlebotomy. Optimising preterm infant iron status after discharge is important as poor iron status has been associated with negative health and neurodevelopmental outcomes later in life. Only preterm infants born before 32 weeks gestation or with a birth weight less than 1800 g currently receive routine iron supplementation after discharge from Auckland City Hospital; however there is paucity of evidence to determine whether this is best practice. Objective: To investigate the iron status of preterm infants in Auckland, New Zealand at four months after discharge from hospital. Methods: Sixty one preterm infants were recruited through Auckland City Hospital. At four months after discharge infant haemoglobin, serum ferritin and soluble transferrin receptor (sTfR) concentrations were measured to assess iron status. Weight, length and head circumference were also measured. Information about iron supplementation and mode of feeding was collected using an online questionnaire. Statistical analysis using independent t-tests, Mann-Whitney tests and bivariate correlations were performed. Results: 16.4% of preterm infants had iron deficiency anaemia (defined in paediatric populations as a haemoglobin less than 110 g/L in conjunction with low iron stores) at four months after discharge, with an additional 6.6% of preterm infants classified as having iron deficiency. No infant had iron overload. Iron supplementation was associated with significantly higher haemoglobin (P<0.001) and serum ferritin (P<0.001) concentrations along with lower sTfR concentrations (P=0.005) at four months after discharge. Iron supplementation was also protective against suboptimal iron status at four months after discharge (P=0.018). Mode of feeding, introduction of solids, intrauterine growth restriction, and maternal iron status had no effect on infant iron status at four months after discharge. There was also no relationship between growth and iron supplementation or iron status at four months after discharge. Conclusion: Preterm infants who did not receive iron supplements after discharge had an increased risk of developing iron deficiency and iron deficiency anaemia at four months after discharge. Routine iron supplementation for all preterm infants combined with screening for iron deficiency anaemia after discharge appears to be a safe and effective way to reduce the risk of iron deficiency and iron deficiency anaemia at four months after discharge.