Aim: to determine the independent effect of prenatal tobacco smoke exposure on fetal growth using customized birthweight norms.
Methods: demographic characteristics and data on exposure to tobacco smoke during pregnancy were obtained from singleton neonates ≥ 34 weeks' gestation. Centile Calculator software v62.2 (www.gestation.net) was used for calculating customized birthweight percentiles.
Results: of the 3227 neonates studied, 30.9% were exposed to maternal smoking during pregnancy, whereas involuntary maternal exposure was reported in 20.1%. Growth restriction was noted in 350 (10.8%). The odds ratio (OR) for fetal growth restriction was 1.49 (1.10-1.91) in passive smokers, and 2.34 (1.81-2.96) in smokers. A decrease in birthweight and an increase in the prevalence of growth restriction with the increasing number of cigarette consumption was observed. This effect was evident even in cases of a "minimal" consumption of 1-5 cigarettes per day.
Conclusion: an essential adverse effect of tobacco smoke exposure on fetal growth in pregnancies exposed to passive smoking, as well as in those with "minimal" maternal cigarette consumption, was found. Since approximately 30% of growth restricted neonates could be independently attributed to active or passive maternal exposure, these findings reinforce the need for smoking preventive strategies in pregnant women and their environment.