MATERNAL SMOKING DURING PREGNANCY, URINE COTININE CONCENTRATIONS, ANDBIRTH OUTCOMES - A PROSPECTIVE COHORT STUDY

Background. Most studies of the reproductive consequences of cigarette smoking base exposure on sell-reported smoking habits. This study exa mines the relationship of birth outcomes to the timing and intensity o f maternal active and passive smoking estimated both from self-reports and from cotinine concentration in maternal urine during early, middl e, and late gestation. Method. This cohort study included 740 white an d Hispanic women who obtained antenatal care at the East Boston Neighb orhood Health Center between 1986 and 1992. At each antenatal visit, i nformation on maternal active and passive smoking was obtained by a de tailed questionnaire, and by measurement of urine cotinine concentrati ons. Infant birth outcomes were obtained from hospital records. Multip le linear regression was used to evaluate antenatal smoking variables on birth outcomes, with adjustment for maternal demographic characteri stics, reproductive history, alcohol use, maternal weight end height, and infant gender. Results. The percentage of mothers who ever smoked cigarettes during pregnancy was 55.5% for white and 10.2% for Hispanic women. A significant inverse exposure-response relationship between c otinine concentration in maternal urine and infant size at birth was d emonstrated. However, the relationship was less clear between maternal self-reported smoking status and these outcomes. For the entire gesta tion, a 1000 ng increase in mean urine cotinine concentration was asso ciated with a 59 +/- 9 g reduction in birthweight, a 0.25 +/- 0.05 cm reduction in length, and a 0.12 +/- 0.03 cm reduction in head circumfe rence, respectively. For maternal passive smoking, the much smaller ma gnitude of effect precludes firm conclusions. Conclusions. These data suggest that preventing and reducing active maternal smoking during pr egnancy may have a beneficial impact on infant size at birth.