Background: Poor fetal growth rate, as indicated by lower birth weight, is associated with lower respiratory function in childhood; however, findings in adult life remain inconsistent. A birth cohort provides the opportunity to study the association between birth weight and adult respiratory function.
Methods: The present study data are from a longitudinal birth cohort, the Mater-University of Queensland Study of Pregnancy. Prospective data were available from 2,368 young adults who underwent standard spirometry when 21 years old. Pregnancy and birth-related variables collected were birth weight, placental weight, parental height, maternal educational status, maternal smoking history in pregnancy, and maternal history of alcohol, tea, and coffee consumption during pregnancy. The impact of birth weight on adult lung function was assessed using univariate and multivariate analyses.
Results: For every 100-g increase in birth weight, FVC (95% CI) at 21 years increased by 24 mL (15-32) in men and 20 mL (13-27) in women, and the increase in FEV1 (CI) was 22 mL (15-30) and 16 mL (11-22), respectively. These associations remain after adjusting for lifestyle factors during pregnancy, current smoking, and parental height. However, further adjustment for adult height reduces the strength of association and remains significant for FEV1: 8 mL (1-14) in men and 5 mL (1-10) in women, but not for FVC: 7 mL (-1-14) in men and 5 mL (-1-11) in women.
Conclusion: Our longitudinal cohort study provides evidence of robust links between birth weight and adult lung function at the age of 21 years. Various estimates of the effect size in the literature may be related to the age at assessment.