Antenatal Maternal Smoking and Lung Function in Very Prematurely Born Children

Antenatal exposure to maternal smoking negatively impacts on fetal lung development resulting in infant lung function abnormalities. Lung clearance indices (LCI) were worse in term born infants exposed to antenatal maternal smoking compared to not. Our aim was to assess the effect of antenatal maternal smoking on lung function, in particular LCI, in very prematurely born children.

Lung function testing was undertaken at 11-14 years, when household members smoking and active smoking were assessed. Antenatal maternal smoking had been recorded. Lung function was assessed by LCI, spirometry, plethysmography, gas transfer and fraction of exhaled nitric oxide.

Two hundred and thirty children with a median gestation age of 27 weeks were assessed. Fifty-five had antenatal exposure to maternal smoking. Those with exposure to antenatal maternal smoking were more likely to live with a household member that smoked (67% vs. 18%, p < 0.001). Children of mothers who smoked in pregnancy were also more likely to be active smokers at follow up (indicated by urinary cotinine levels greater than 15 ng/mL) (49% vs. 7%; p < 0.001). Lung clearance index was higher in children exposed to maternal smoking in pregnancy (mean (SD): 7.8 (1.1) vs. 7.4 (1.2); mean difference (95% CI): -0.44 (-0.91, 0.02); p = 0.031). There were no significant differences in other measures of lung function.

Very prematurely born children exposed to antenatal maternal smoking had greater ventilation inhomogeneity and were more likely to be active smokers and live with a household member that smoked. These findings were not explained by active smoking or household smoking contact at follow up, but those who had BPD had greater ventilation inhomogeneity.