Exclusively breastmilk-fed infants gained less weight compared with formula-fed infants. SDS for weight decreased between birth and discharge (median (Q1-Q3): formula -0.9 (-1.4 to [-0.5]) vs breastmilk -1.1 (-1.7 to [-0.6])). Exclusive formula feeding of very low birth weight infants was associated with increased risks of BPD (OR 2.6) as well as NEC (OR 12.6) and ROP (OR 1.80) after controlling for known risk factors.