Association of smoking during pregnancy and fetal growth restriction: subgroups of higher susceptibility

OBJECTIVE: To analyze the association between maternal smoking and fetal growth restriction, defined as a failure to achieve the growth potential, and to define subgroups of higher susceptibility for this association. STUDY DESIGN: A definition of growth restriction by customized birthweight standards applied to 13,661 non-malformed singleton deliveries. Customization was performed by maternal ethnic origin, height, booking weight, parity, gestational age at delivery and fetal gender. The adjusted risk of smoking for customized smallness-for-gestational age and the identification of subgroups with higher susceptibility were assessed by logistic regression. RESULTS: Overall, the adjusted odds ratio of smoking (all levels of exposure grouped) for the occurrence of growth restriction was 1.9 (95% confidence interval: 1.69-2.13). Smoking was etiologically responsible for 13.9% (95% confidence interval: 11.2-16.5) of the cases of growth restriction occurring in the population. Smoking resulted in an increasingly greater risk of growth restriction with progressive levels of cigarette consumption. The risk of smoking for fetal growth restriction was significantly greater in older women and those with a previous history of spontaneous preterm delivery. CONCLUSIONS: Smoking is associated with a higher risk for growth restriction. In addition, older pregnant women and those with a previous history of preterm delivery have an increased susceptibility.