American Journal of Epidemiology Advance Access published online on July 24, 2008
American Journal of Epidemiology, doi:10.1093/aje/kwn175
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Original Contribution |
Maternal Smoking during Pregnancy and Children's Cognitive and Physical Development: A Causal Risk Factor?
1 Department of Society, Human Development, and Health, Harvard School of Public Health, Boston, MA
2 Department of Epidemiology, Harvard School of Public Health, Boston, MA
3 Department of Neurology, Miller School of Medicine, University of Miami, Miami, FL
4 Department of Community Health, Brown University, Providence, RI
Correspondence to Dr. Stephen E. Gilman, Department of Society, Human Development, and Health, Harvard School of Public Health, 677 Huntington Avenue, Boston, MA 02115 (e-mail: sgilman{at}hsph.harvard.edu).
Received for publication February 25, 2008. Accepted for publication May 21, 2008.
There remains considerable debate regarding the effects of maternal smoking during pregnancy on children's growth and development. Evidence that exposure to maternal smoking during pregnancy is associated with numerous adverse outcomes is contradicted by research suggesting that these associations are spurious. The authors investigated the relation between maternal smoking during pregnancy and 14 developmental outcomes of children from birth through age 7 years, using data from the Collaborative Perinatal Project (1959–1974; n = 52,919). In addition to adjusting for potential confounders measured contemporaneously with maternal smoking, the authors fitted conditional fixed-effects models among siblings that controlled for unmeasured confounders. Results from the conditional analyses indicated a birth weight difference of –85.63 g associated with smoking of 
20 cigarettes daily during pregnancy (95% confidence interval: –131.91, –39.34) and 2.73 times' higher odds of being overweight at age 7 years (95% confidence interval: 1.30, 5.71). However, the associations between maternal smoking and 12 other outcomes studied (including Apgar score, intelligence, academic achievement, conduct problems, and asthma) were entirely eliminated after adjustment for measured and unmeasured confounders. The authors conclude that the hypothesized effects of maternal smoking during pregnancy on these outcomes either are not present or are not distinguishable from a broader range of familial factors associated with maternal smoking.
child; child development; cognition; growth; intelligence; pregnancy; smoking
Abbreviations: CI, confidence interval; CPP, Collaborative Perinatal Project; GEE, generalized estimating equations; IQ, intelligence quotient; WRAT, Wide Range Achievement Test