The Impact of Small-for-Gestational-Age on Pulmonary Function in Infancy, a Retrospective Cohort Study

Background: Low-birth-weight percentile has been associated with impaired pulmonary function at adulthood. However, its impact on pulmonary function early in life remains less well established. Objective: To assess the impact of small-for-gestational-age (SGA) status on pulmonary function in infants 3 months to 2 years of age. Methods: We conducted a single-center retrospective cohort study evaluating infant pulmonary function tests (iPFTs) performed at Hadassah medical center between 2008 and 2023. Tests were performed as part of routine clinical evaluation following referral for respiratory symptoms. 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. Results: iPFT data from 161 SGA infants were compared with 545 AGA/LGA infants. No consistent significant differences were found between the groups (mean (SD); FEV_0.5 = 80.11 (18.40) %predicted vs. 81.55 (18.03) %predicted, P = 0.40; FVC = 84.24 (20.30) %predicted vs. 85.61 (20.22) %predicted, P = 0.47). SGA infants were not more likely to demonstrate restrictive (8.3% vs. 4.7%, P = 0.09) or obstructive (53.7% vs. 49.7%, P = 0.40) patterns. Findings were similar in analyses stratified by prematurity and term birth. Conclusions: Our findings challenge the hypothesis that SGA is associated with impaired pulmonary function in infancy. While subtle differences were observed, they were not statistically or clinically significant. However, as this cohort consisted of symptomatic infants, the findings may not be generalizable to the broader infant population. Population-based studies are needed to further clarify the respiratory outcomes of intrauterine growth restriction.