Highest Plasma Phenylalanine Levels in (Very) Premature Infants on Intravenous Feeding; A Need for Concern

OBJECTIVE: To analyse the association in newborns between blood levels of phenylalanine and feeding method and gestational age. STUDY DESIGN: This observational, cross-sectional study included a sample of 11,829 infants between 2008 and 2013 in a Spanish region. Data were recorded on phenylalanine values, feeding method [breast, formula, mixed (breast plus formula), or partial or fully intravenous feeding], gestational age in weeks (<32, 32–37, ≥37), gender and days since birth at the moment of blood collection. Outcomes were [phenylalanine] and [phenylalanine] ≥95th percentile. Associations were analysed using multivariate models [linear (means difference) and logistic regression (adjusted odds ratios)]. RESULTS: Higher phenylalanine values were associated with lower gestational age (p<0.001) and with intravenous feeding (p<0.001). CONCLUSION: The degree of prematurity and intravenous feeding influenced the plasma concentration of phenylalanine in the newborn. Caution should be taken in [phenylalanine] for newborns with intravenous feeding, monitoring them carefully. Very preterm infants given the recommended amount of amino acids should also be strictly monitored. These findings should be taken into consideration and call for adapting the amounts to the needs of the infant.