Article

Maternal smoking during pregnancy and children’s cognitive and physical development: A causal risk factor?

Department of Society, Human Development, and Health, Harvard School of Public Health, Boston, MA 02115, USA.
American journal of epidemiology (Impact Factor: 4.98). 09/2008; 168(5):522-31. DOI: 10.1093/aje/kwn175
Source: PubMed

ABSTRACT 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 >or=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.

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    • "There is mixed evidence on the effects of maternal smoking and alcohol consumption during pregnancy on child outcomes, with some arguing it lowers outcomes and others finding no effect (see e.g. Olds et al., 1994; Gilman, Gardener and Buka 2008; Kafouri et al., 2009; Davey Smith, 2008; Nilsson, 2008; Russell, 1991). "
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    ABSTRACT: Height has long been recognised as associated with better outcomes: the question is whether this association is causal. We use children’s genetic variants as instrumental variables (IV) to deal with possible unobserved confounders and examine the effect of child and adolescent height on a wide range of outcomes: academic performance, IQ, self-esteem, symptoms related to depression and behavioural problems, including hyperactivity, emotional, conduct and peer problems. OLS findings show that taller children have higher IQ scores, perform better in school tests, and are less likely to have emotional or peer problems. The IV results differ. They show that taller children have better cognitive performance but, in contrast to the OLS, indicate that taller children are more likely to have behavioural problems. The magnitude of these IV estimates is large. For example, the effect of one standard deviation increase in height on IQ is comparable to the IQ difference for children born approximately 6 months apart within the same school year, while the increase in hyperactivity is comparable to the raw difference in hyperactivity between boys and girls.
    European Economic Review 01/2013; 57. DOI:10.1016/j.euroecorev.2012.09.009 · 1.53 Impact Factor
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    • "Hence, while some studies reported lower IQ scores in exposed individuals [16] [17] [18] [19] [20], others reported significant associations to disappear after adjustment for confounders [21] [22] [23] [24], and yet others found no association [25]. The overall conclusion regarding the effects of smoking in pregnancy on offspring intelligence thus remains ambiguous, and it is widely debated whether previously reported associations reflect causal relations or rather methodological shortcomings, such as residual confounding [23] [26]. "
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    ABSTRACT: The aim of the study was to examine the effects of tobacco smoking in pregnancy on children's IQ at the age of 5. A prospective follow-up study was conducted on 1,782 women, and their offspring were sampled from the Danish National Birth Cohort. At 5 years of age, the children were tested with the Wechsler Preschool and Primary Scale of Intelligence-Revised. Parental education, maternal IQ, maternal alcohol consumption in pregnancy, the sex and age of the child, and tester were considered core confounders, but the full model also controlled for prenatal paternal smoking, maternal age and Bodymass Mass Index, parity, family/home environment, postnatal parental smoking, breast feeding, the child's health status, and indicators for hearing and vision impairments. Unadjusted analyses showed a statistically significant decrement of 4 points on full-scale IQ (FSIQ) associated with smoking 10+ cigarettes per day compared to nonsmoking. After adjustment for potential confounders, no significant effects of prenatal exposure to tobacco smoking were found. Considering the indisputable teratogenic effects of tobacco smoking, these findings should be interpreted with caution. Still, the results may indicate that previous studies that failed to control for important confounders, particularly maternal intelligence, may be subject to substantial residual confounding.
    Journal of pregnancy 12/2012; 2012:945196. DOI:10.1155/2012/945196
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    • "Two compelling lines of evidence support both sides of the debate. Quasi-experimental designs which can control for genetic relatedness have supported the genetic transmission hypothesis (Thapar et al. 2009; D'Onofrio et al. 2008, 2010; Maughan et al. 2004; Gilman et al. 2008; Silberg et al. 2003), whereas research in animal models clearly demonstrates a deleterious impact of smoking exposure on brain development supporting the teratogenic hypothesis (for reviews see Baler et al. 2008; Wakschlag et al. 2002). Building on foundational work by Krueger to model the multidimensional nature of problem behavior (Krueger et al. 2002, 2007), the present study used CFA to test the strength of the relationship between maternal prenatal smoking and problem behavior clusters. "
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    ABSTRACT: This study illustrates the application of a latent modeling approach to genotype-phenotype relationships and gene × environment interactions, using a novel, multidimensional model of adult female problem behavior, including maternal prenatal smoking. The gene of interest is the monoamine oxidase A (MAOA) gene which has been well studied in relation to antisocial behavior. Participants were adult women (N = 192) who were sampled from a prospective pregnancy cohort of non-Hispanic, white individuals recruited from a neighborhood health clinic. Structural equation modeling was used to model a female problem behavior phenotype, which included conduct problems, substance use, impulsive-sensation seeking, interpersonal aggression, and prenatal smoking. All of the female problem behavior dimensions clustered together strongly, with the exception of prenatal smoking. A main effect of MAOA genotype and a MAOA × physical maltreatment interaction were detected with the Conduct Problems factor. Our phenotypic model showed that prenatal smoking is not simply a marker of other maternal problem behaviors. The risk variant in the MAOA main effect and interaction analyses was the high activity MAOA genotype, which is discrepant from consensus findings in male samples. This result contributes to an emerging literature on sex-specific interaction effects for MAOA.
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