Background: Human milk feeding (HMF) is associated with a reduced risk of developing bronchopulmonary dysplasia, but studies investigating its effect on long-term lung function are lacking.

Aims: To evaluate the dose-dependent impact of human milk consumption on lung function in extremely low-birth-weight (ELBW) preterm infants over the first two years of corrected age (CA).

Methods: We conducted a retrospective study of infants with a birth weight (BW) <1000g who had lung function assessment by tidal-breathing flow-volume loop (TBFVL) analysis at 0-3, 3-6, 6-12, 12-18 and 18-24 months' CA (June 2009 - June 2020). Among TBFVL parameters, we considered tidal volume (Vt) and time to peak expiratory flow to expiratory time (tPTEF/Te) as a marker of airway obstruction.

Main results: 180 infants were included, with a mean (SD) GA 26.5 (1.90) weeks, BW 772.4 (147.0) g. According to a general linear model including gestational age(GA), being small for GA (SGA), sex, human milk percentage, sepsis and BPD, lower gestational age and being SGA were associated with worse tPTEF/tE at 0-3 months CA (p 0.039 and 0.013 respectively). A higher percentage of human milk out of the total enteral intake was associated with better tPTEF/tE z-scores at 0-3 months (p 0.004) and 18-24 months of CA (p 0.041). BPD diagnosis was associated with a relevantly worse tPTEF/tE z-score at 6-12 months of CA (p 0.003). 

Conclusions: Infants with higher HM consumption had significantly reduced airway obstruction across the first two years' CA, suggesting that HMF may contribute dose-dependent to improve lung function in former ELBW preterm infants.