The association between low birth weight and pulmonary function in infants

<bold>Background:</bold> Low birth weight has been shown to be associated with impaired pulmonary function at adulthood. However, little is known about its effect on pulmonary function early in life. <bold>Objective:</bold> To assess the impact of small-for-gestational-age (SGA) status on pulmonary function in infants 3 months to 2 years of age. <bold>Methods:</bold> We conducted an observational study evaluating infant pulmonary function tests (iPFTs) performed at our center between 2008 and 2023. iPFTs results in infants born SGA were compared with infants born appropriate and large for gestation age (AGA/LGA). Excluded from the study were infants diagnosed with chronic diseases other than prematurity. <bold>Results:</bold> iPFT data from 161 SGA born infants (57% male, age (mean (SD)) = 12.18 (7.34) months) were compared with 545 infants born AGA/LGA (67% male, age (mean (SD)) = 10.72 (6.21) months). No consistent significant differences were found in iPFT results between infants born SGA and infants born AGA/LGA (mean (SD); FEV0.5 = 80.11 (18.40) %predicted Vs. 81.55 (18.03) %predicted, p=0.39; FVC = 84.24 (20.30) %predicted Vs. 85.61 (20.22) %predicted, p=0.46; FRC = 98.18 (22.80) %predicted Vs. 101.50 (26.89) %predicted, p=0.16). Infants born SGA were not more likely to suffer from a restrictive (8.3% vs 4.7%, p=0.09) or an obstructive phenotype (53.7% vs. 49.7%, p=0.39). This remained true when evaluating subgroups of early premature and term born infants. <bold>Conclusions:</bold> Our results do not support the hypothesis that low birth weight is associated with impaired pulmonary function at infancy. Further studies evaluating healthy infants and children are required to fully understand the effect of low birth weight on respiratory health in children and adults.