Objectives: Poor growth after preterm birth is associated with impaired neurodevelopmental outcome. Limited evidence indicates that breast fed infants have improved neurodevelopmental outcomes but slower growth. We aimed to evaluate weight gain and head growth between birth and term in relation to breast milk intake, allowing for illness severity.Methods: We studied inborn infants delivered at or below 32 weeks gestation who remained in our neonatal unit up to 37 weeks postmenstrual age. We expressed weight and head circumference (HC) as standard deviation score (SDS), growth between birth and discharge as SDS gain (SDSG), and illness severity and breast milk exposure as the number of days of level 1 (full) intensive care (%L1IC) and the number of days breast milk was received (%BM) as a percentage of days from birth to discharge.Results: Poor postnatal weight gain was accompanied by accelerated head growth There was a highly significant fall in weight SDS between birth and discharge (mean (SD) weight SDS, birth -0.31 (0.96), discharge -1.32 (1.02), p<0.001) and a highly significant increase in HC SDS (mean (SD) HC SDS, birth -0.52 (0.95), discharge -0.03 (1.25), p=0.003). %L1IC had a highly significant negative impact upon weight SDSG (p=0.006) and %BM had a significant positive impact upon HC SDSG (p=0.043).Conclusion: Accelerated postnatal head growth suggests catch-up after antenatal restraint. As this appears facilitated by breast milk, there is an urgent need to evaluate the optimal use of breast milk in preterm neonates. Illness severity is a significant determinant of poor postnatal weight gain.