Effects of smoking in pregnancy on neonatal lung function

Aims-To assess the effects of smoking during pregnancy on lung mechanics and lung volumes in the immediate neonatal period, before infants are exposed to passive smoking. Methods-Lung function tests were carried out within 72 hours of delivery in infants born to 100 non-smoking and 189 smoking mothers. Lung growth was assessed by plethysmography and lung mechanics using the single breath occlusion technique and oesophageal balloon/pneumotachography. Antenatal maternal serum cotinine values were obtained from 133 mothers. Results-Smoking was associated with a significant reduction in birthweight (mean 256 g, 95% CI 0.164 to 0.392), and length (mean 1.26 cm, 95% CI 0.48 to 2.00). Lung volume was not reduced when related to weight. Smoking was associated with a highly significant reduction in static compliance (C-rs). This effect remained significant after relating C-rs to weight and lung volume. Regression analyses showed that the C-rs association was limited to the boys. Smoking was associated with a small but significant reduction in respiratory system conductance (G(rs)) (single breath occlusion technique) and total pulmonary conductance (G(p)). These associations were Limited to girls. Conclusions-Smoking in pregnancy reduces static compliance in boys and conductance in girls. There was no evidence that maternal smoking adversely affected fetal lung growth.