Impact of breast milk intake on body composition at term in very preterm babies: secondary analysis of the Nutritional Evaluation and Optimisation in Neonates randomised controlled trial.

OBJECTIVE: To investigate the impact of breast milk (BM) intake on body composition at term in very preterm infants. DESIGN: Preplanned secondary analysis of the Nutritional Evaluation and Optimisation in Neonates Study, a 2-by-2 factorial randomised controlled trial of preterm parenteral nutrition (PN). SETTING: Four National Health Service hospitals in London and South-East England. PATIENTS: Infants born at <31 weeks of gestation; infants with life-threatening congenital abnormalities and those unable to receive trial PN within 24 hours of birth were ineligible. 133 infants survived and underwent whole-body MRI at term (37-44 weeks postmenstrual age). MAIN OUTCOME MEASURES: Non-adipose tissue mass (non-ATM), ATM and ATM as a percentage of body weight (% ATM) at term. RESULTS: Compared with the exclusively BM group (proportion of BM=100% milk, n=56), predominantly formula-fed infants (BM ≤50%, n=38) weighed 283.6 g (95% CI 121.6 to 445.6) more, had 257.4 g (139.1-375.7) more non-ATM and a greater positive weight Z-score change between birth and term. There were no significant differences in weight, non-ATM and weight Z-score change between the exclusively and predominantly BM (BM 51%-99%, n=39) groups. Compared with the exclusively BM group no significant differences were observed in ATM and %ATM in the predominantly BM and predominantly formula-fed groups. CONCLUSIONS: The slower weight gain of preterm infants fed BM appears to be due to a deficit in non-ATM and may reflect lower protein intake. Whether this pattern persists into childhood, is altered by BM fortification or later diet, or relates to functional outcomes, are important research questions. CLINICAL TRIAL REGISTRATION: ISRCTN29665319, post results.