Introduction: The detrimental effect of birth at <32 weeks? gestation on lung function is well established. However, the effect of moderate-late preterm (32 to <37 weeks? gestation; MLP) birth on lung function during childhood remains unclear.
Aim: To assess the effect of being born MLP, compared with being born at term, on lung function at 9 years of age.
Methods: Prospective cohorts of children born either a) MLP or b) at term in the Royal Women?s Hospital, Victoria, Australia. Participants completed spirometry, diffusing capacity for carbon monoxide (DLCO), body plethysmography and nitrogen multiple breath washout (N2MBW) at 9 years of age. Mean differences in z-scores of lung function outcomes between those born MLP and at term were estimated using linear regression models with adjustment for potential confounding.
Results: 149 children born MLP and 77 term controls with a mean (SD) age of 9.9 (0.4) and 9.7 (0.3) years, respectively, underwent lung function testing (Table 1).
Table 1. Mean differences in lung function z-scores between children born MLP and term.
| Variable | MD (95% CI) |
| FEV1 | -0.46 (-0.88, -0.036) |
| FVC | -0.43 (-0.83, -0.03) |
| FEV1/FVC | 0.03 (-0.43, 0.49) |
| DLCO | -0.19 (-0.52, 0.13) |
| Total lung capacity (TLC) | -0.52 (-0.84, -0.21) |
| Functional residual capacity | -0.28 (-0.54, -0.03) |
| Residual volume (RV) | -0.12 (-0.33, 0.09) |
| RV/TLC | -0.03 (-0.27, 0.2) |
| Lung clearance index 2.5% | 0.04 (-0.62, 0.69) |
MD: mean difference; CI: confidence interval
Conclusion: This study provides evidence that children born MLP have worse expiratory volumes compared with term-born controls. These differences are likely explained by smaller overall lung volumes, reflected by lower TLC, as opposed to a pattern of airflow obstruction.