Objective To evaluate a quality improvement (QI) programme to increase the use of maternal breast milk (MBM) in preterm infants.

Design Interrupted time series analysis.

Setting 17 neonatal units in the East of England (EoE) Perinatal Network; 144 in the rest of the UK Neonatal Collaborative (UKNC).

Patients Infants born ≤32⁺⁶ weeks gestation admitted to neonatal care between 2009 and 2012.

Intervention A ‘care bundle’ to promote MBM in the EoE.

Outcomes Percentage of infants receiving exclusive or any MBM at discharge and care days where any MBM was received.

Methods Data were extracted from the National Neonatal Research Database; outcomes were compared preintervention and postintervention, and in relation to the rest of the UKNC.

Results Exclusive and any MBM use at discharge increased from 26% to 33% and 50% to 57% respectively in the EoE, though there was no evidence of a step or trend change following the introduction of the care bundle. Exclusive MBM use at discharge improved significantly faster in EoE than the rest of the UKNC; 0.22% (95% CI 0.11 to 0.34) increase per month versus 0.05% (95% CI 0.01 to 0.09, p=0.007 for difference). The percentage of infants receiving MBM at discharge and care days where any MBM was received was not significantly different between EoE and the rest of the UKNC.

Conclusions This QI programme was associated with some improvement in MBM use in preterm infants that would not have been evident without the use of routinely recorded national comparator data.