Diaphragm ultrasound and lung aeration in small-for-gestational-age versus appropriate-for-gestational-age newborns: a cross-sectional study

Objective To compare diaphragm ultrasound findings and lung aeration between SGA and AGA newborns. Methods In this cross-sectional study, clinically stable term SGA and AGA newborns underwent diaphragm and lung ultrasound. Diaphragm parameters and 6-region lung ultrasound score (LUS) were assessed, with thickness and excursion normalized by birth weight. Results Fifty-four newborns were included (27 SGA and 27 AGA). SGA newborns had lower absolute inspiratory and expiratory diaphragmatic thicknesses; however, these between-group differences were no longer significant after normalization by birth weight. Regression analyses adjusting for body weight continued to demonstrate an association between SGA status and diaphragmatic thickness. No significant differences were observed in diaphragmatic functional indices or pulmonary aeration. Conclusions SGA newborns had lower absolute diaphragmatic thickness than AGA newborns, while diaphragmatic function and pulmonary aeration were preserved. Differences in thickness were influenced by body size but were not fully explained by birth weight.