Passive and active maternal smoking during pregnancy, as measured by serum cotinine, and postnatal smoke exposure. I. Effects on physical growth at age 5 years.

The authors evaluated the effect of maternal environmental tobacco smoke (ETS) exposure during pregnancy and prenatal maternal smoking on child's height at age 5 years, using serum cotinine as a biomarker of exposure. They also determined the effects of postnatal smoke exposure. Participants included 2,622 women enrolled in the Child Health and Development Studies between 1964 and 1967. Nonsmokers were divided into ETS-exposed (serum cotinine 2-10 ng/ml; n = 77) and not exposed (n = 1,610), and smokers (n = 935) were divided into tertiles based on serum cotinine levels: 0-79, 80-163, and 164-569 ng/ml. Multivariate models adjusting for race, sex, birth order, and maternal height, body mass, education, and age indicated that children of smokers were 0.3, 0.3, and 0.8 cm shorter in the lowest, middle, and highest tertile of serum cotinine, respectively, and children of ETS-exposed women were 0.5 cm taller than those of nonsmokers. Only the children of heavy smokers were significantly shorter than children of nonsmokers; however, this difference disappeared after controlling for birth weight and gestational age. The adjusted heights of children of women who smoked both during and after pregnancy were significantly shorter than those of children of nonsmokers, but this effect also disappeared after controlling for birth weight and gestational age. These results suggest that the effects of smoke exposure on children's height may be explained by the effects of maternal smoking on fetal growth.