Maternal Smoking And Cognitive Development

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Written and compiled by Wanda Hamilton

While some researchers have suggested that maternal smoking during pregnancy impedes the offsprings' later cognitive development, many others have found no such link after they have adjusted for socio-economic class and other risk factors. By far the majority of research in this area has implicated low socio-economic class as the greatest risk factor for poor cognitive development. In addition, countless studies have been done on Fetal Alcohol Syndrome and the effect of excessive maternal drinking during pregnancy on the poor cognitive development of children.

"However, after adjustment for confounding covariates, the results showed no detectable relationship between smoking during pregnancy and child cognitive ability. These results suggest that children whose mothers smoked during pregnancy fared worse on tests of cognitive ability not because of possible causal effects of smoking, but rather because these children tended to come from families which provided a relatively disadvantaged home environment."

Fergusson DM, Lloyd M, "Smoking during pregnancy and its effects on child cognitive ability from the ages of 8 to 12 years," Christchurch Child Development Study, Dept. of Paediatrics, Christchurch School of Medicine, New Zealand. Paediatric Perinatal Epidemiology, Apr 1991; 5(2):189-200.

"However, smoking by mothers during pregnancy was not significantly related to scores in cognitive tests."

Niemela A, Jarvenpaa AL, Children's Hospital, University of Helsinki, Finland, "Is breastfeeding beneficial and maternal smoking harmful to the cognitive development of children?" Acta Paediatr, Oct l996;85(10):1202-1206.

"After controlling for levels of background disadvantage, no relationship was found between reports of smoking and language, cognitive or physical development."

McGee R, Stanton WR, "Smoking in pregnancy and child development to age 9 years," J Paediatr Child Health, Jun l994;30(3):263-268.

"The differences in mean developmental test scores between children whose mothers smoked and those of mothers who did not smoke were slight. . . .These differences were not statistically significant after adjustment for socio-economic status, quality of home environment and mother's intelligence, suggesting that the social and environmental factors are major confounders of the association of exposure to maternal smoking and neuropsychological development in childhood."

Baghurst PA, Tong SL, Woodward A, McMichael AJ, "Effects of maternal smoking upon neurophychological development in early childhood: importance of taking account of social and environmental factors," Paediatr Perinat Epidemiology, Oct l992;6(4):403-415.

"The authors sought to determine the neurobehavioral effects of prenatal exposure to maternal active smoking and environmental tobacco smoke (ETS), assessed by maternal serum cotinine level, and of postnatal exposure to smoke based on maternal report. Five-year-old children (n = 2,124) who were participants in the Child Health and Development Studies in Oakland, California, between 1964 and l967 were evaluated with the use of the Peabody Picture Vocabulary Test (PPVT) and the Raven Coloured Progressive Matrices Test. . . .Children of ETS-exposed women did not differ from children of other nonsmokers on neurobehavioral assessment. Children whose mothers smoked during pregnancy had somewhat higher adjusted Raven (p = 0.10) and PPVT scores (p = 0.06) than children of nonsmokers, although they did not differ in their activity level (p = 0.06)." In other words, children whose mothers smoked during pregnancy did somewhat better on standard cognitive development tests than children of nonsmokers, and there was no difference in performance between children whose mothers had been exposed to ETS and those whose mothers hadn't been so exposed.

Eskenazi G, Trupin LS, Maternal and Child Health Program, School of Public Health, University of California, Berkeley, "Passive and active maternal smoking during pregnancy, as measured by serum cotinine, and post natal smoke exposure. II. Effects on neurodevelopment at age 5 years," Am J Epidemiol, Nov l995; 142 (9 Suppl):S19-S29.

". . . univariate and stepwise multiple regression analyses did not identify a significant negative association between cigarette smoking and 1 or 5-minute Apgar scores." This was a study of 1,709 mother/child pairs at Boston City Hospital.

Hingson R, Gould JB, Morelock S, Kayne H, Heeren T, Alpert JJ, Zuckerman B, Day N, "Maternal cigarette smoking, psychoactive substance use, and infant Apgar scores," Am J Obstet Gynecol, Dec 15 l982; 144(8):959-966.

"Evidence for FAS [fetal alcohol syndrome], impaired intrauterine growth, birth defects, and mental retardation related to alcohol is compelling; evidence for alcohol-induced adverse behaviors and impaired speech is tenuous. Teratogenic, cognitive, or behavioral effects associated with prenatal exposure to marijuana, cigarettes, cocaine, or opiates have not been well established."

Chiriboga CA, Dept of Neurology, Columbia University College of Physicians and Surgeons, "Fetal effects," Neurol Clin, Aug 1993; 11(3):707-728.

"There was no evidence that the cognitive devlopment of low birthweight children was more sensitive to a non-optimal childrearing environment that that of normal birthweight children. These findings indicate that the risk of impaired cognitive development increases with decreasing socioeconomic status, and that this risk is much larger than, and independent of, the small risk attributable to low birthweight."

Sommerfelt K, Ellertsen B, Markestad T, "Parental factors in cognitive outcome of non-handicapped low birthweight infants," Arch Dis Chld Fetal Neonatal Ed, Nov l995; 73(3):F135-F142.

"Low socioeconomic status of the family (SES) accounted for 44-50% of mental retardation and a low level of maternal education accounted for 20%. Other prenatal factors with significantly elevated relative risks, (P< 0.05) were maternal IQ score less than 70, weight gain in pregnancy less than 10 pounds and multiple birth. Maternal anemia in pregnancy accounted for 14% of mental retardation in blacks, and, urinary tract infections accounted for 6% of mental retardation in whites. "

Camp BW, Broman SH, Nichols PL, Leff M, "Maternal and neonatal risk factors for mental retardation: defining the 'at-risk' child," Early Hum Dev, Jan 9 l998; 50(2):159-173. "There is little evidence, however, linking maternal smoking and increased rates of children's behavior problems."
Weitzman M, Gortmaken S, Sobol A, "Maternal smoking and behavior problems of children," Pediatrics, Sep l992; 90(3):342-9. [CDC bib, l992-93, p. 75]

"Even though the association between maternal smoking and delinquency of the offspring remained after adjustment for the available social and demographic factors, maternal smoking may be symptomatic of a certain lifestyle and norm-breaking behaviour which is likely to increase delinquency in the children rather than being an agent with a direct causal role. This is supported by the lack of any clear dose-response pattern and the minor importance of stopping smoking. "

Rantakallio P, Laara E, Isohanni M Moilanen I, "Maternal smoking during pregnancy and delinquency of the offspring: an association without causation?" International Journal of Epidemiology, Dec l992; 21(6):1106-1113

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