Longitudinal study of smoking cessation before pregnancy and children's cognitive abilities at 56 months of age

Abstract

Background An inverse relationship exists between the rates of maternal smoking during pregnancy and children's cognitive abilities. The effect of maternal cessation of smoking before pregnancy on child's cognitive development is less clear. Aims To study whether maternal cessation of smoking before pregnancy is associated with children's cognitive abilities. Study design and subjects The original cohort included all 1535 live-born infants admitted to the neonatal wards during 1 year and 658 randomly recruited non-admitted infants. The present study sample comprised 1019 (68.2%) children of the original sample born at term and free of any major impairment followed up to 56 months. Outcome measures Child's general reasoning, visual–motor integration, verbal competence, and language comprehension at 56 months of age. Results The results showed that children whose mothers smoked > 10 cigarettes per day before pregnancy but none during pregnancy, fared 12.07 (95% confidence interval [CI]: 4.07 to 20.08) and 11.23 (95% CI: 2.81 to 19.66) age-standardized points poorer in general reasoning and in language comprehension tests, respectively, than children of never-smokers. All results were adjusted for the sex, gestational age-adjusted birth weight, multiple/singleton pregnancy, birth order, preeclampsia, maternal diabetes, admission to neonatal ward, 5-minute Apgar score (< 7), breastfeeding, parental level of education, maternal age, BMI at the end of pregnancy and single parenting. Conclusions Heavy smoking before pregnancy is associated with children's lower cognitive abilities even if the mother has quit smoking before pregnancy. Identification and intervention of heavy smoking women of fertile age would potentially improve not only their odds to become pregnant but also benefit the offspring's cognitive functioning.