Formula milk versus donor breast milk for feeding preterm or low birth weight infants.

Systematic review of eight trials including 1017 infants, mostly clinically stable preterm infants with gestational age less than about 32 weeks and/or birth weight less than about 1800 g. The studies evaluated formula milk versus donor breast milk in neonatal care settings when maternal breast milk was unavailable or insufficient.

Formula milk was compared with donor human breast milk across eight trials in preterm or low birth weight infants. Regimens varied by trial and included term formula milk, preterm formula milk, and formula used as a supplement to maternal expressed breast milk; durations ranged from about 4 weeks to hospital feeding periods, with some protocols advancing feeds to 160 to 200 ml/kg/day.

Formula milk produced better short-term growth than donor breast milk, but it also increased the risk of necrotising enterocolitis. Across pooled analyses, formula increased weight gain by 2.59 g/kg/day, crown-heel length by 1.14 mm/week, crown-rump length by 0.59 mm/week, femoral length by 0.34 mm/week, and head circumference by 1.25 mm/week. The risk of necrotising enterocolitis was higher with formula milk, with an overall estimate of 2.46 [1.19, 5.08]; feed intolerance or diarrhoea was also increased, while mortality and invasive infection were not clearly different. The review noted that evidence for formula versus nutrient-fortified donor milk was limited, which reduces applicability to current practice.

Most trials were older, small, and heterogeneous in formula type, feeding protocol, and whether donor milk was fortified or unfortified. Evidence on nutrient-fortified donor milk was limited, so the findings may not fully reflect current neonatal feeding practice. Developmental outcomes and some adverse outcomes were sparsely reported.