Is additional oral phosphate supplementation for preterm infants necessary: an assessment of clinical audit

Adequate phosphate intake is important for the prevention of metabolic bone disease in preterm infants. The European Society for Paediatric Gastroenterology, Hepatology and Nutrition recommends a daily phosphate intake of 184-230 mg/kg/day, which should be met by standard feed volumes of either commercially fortified breast milk or preterm formulae. We sought to investigate whether our local practise of providing supplemental oral phosphate for all infants born before 32 weeks' gestation continues to be necessary. Details of parenteral and milk feeding and both oral and parenteral phosphate supplementation from birth until 8 weeks of age were collected retrospectively from the case notes of 31 preterm infants. Routinely collected biochemical markers of bone mineral status were also recorded. Mean (SD) plasma phosphate concentration was higher when oral phosphate supplementation was given [2.10 (0.38) versus 1.92(0.50) mM/L without supplement (p < 0.001)]. A minimum average phosphate intake of 184 mg/kg/day was achieved by 47 and 77 % of babies in weeks 1 and 2, respectively, and by 84-100 % of infants from week 3. The percentage of plasma phosphate measurements below the minimum target of 1.8 mM/L was greater amongst unsupplemented babies (45 versus 18 %).

A majority of infants <32 weeks' gestation did not achieve the recommended phosphate intake during the first week of life. Despite achieving the recommended phosphate intake from week 3, many infants did not have plasma phosphate concentrations within the accepted normal range. Additional oral supplementation may help to achieve blood phosphate concentrations within this target range.