- OBJECTIVE: To compare neurodevelopmental outcomes of preterm infants at 18-21 months corrected age (CA) whose mothers smoked during pregnancy to those whose mothers did not smoke. STUDY DESIGN: Preterm infants born at <29 weeks of gestation and evaluated at 18-21 months CA were included. Primary outcome was a composite outcome of death or neurodevelopmental impairment (NDI). RESULTS: Of a total of 2760 infants, 699 met exclusion criteria. Of the remaining 2061 infants, 280 (13.6%) were exposed to maternal smoking and 1781 (86.4%) were not. The odds of the composite outcome of death or NDI (aOR 1.40; 95% CI: 1.03-1.91), NDI alone (aOR 1.43; 95% CI: 1.01-2.03), and Bayley-III motor score <85 (aOR 1.91; 95% CI: 1.31-2.81) were higher in exposed infants. CONCLUSIONS: Exposure to maternal smoking was associated with adverse composite outcome of death or NDI, NDI alone and lower motor scores at 18-21 months CA.