Association between changes in smoking habits in subsequent pregnancy and infant birth weight in West Virginia.

West Virginia has one of the highest prenatal smoking prevalence rates in the nation. While overall national prenatal smoking rates have been declining, the prevalence rates in West Virginia continue to climb. Smoking in pregnancy has been associated with deleterious health outcomes in infants, including decreased birth weight. Yet, minimal research has been done on changes in smoking behaviors over time and the association of the changes in infant birth weights. The aim of the current study is to examine the change in prenatal smoking status of West Virginia women and the associated changes in infant birth weights. Population-based secondary data analysis was conducted using West Virginia birth certificates for all singleton infant siblings born between 1989 and 2006, linked based on mother. Infants born to women who smoked during pregnancy had significantly lower birth weights than infants born to non-smokers. Repeated measures analysis used to examine the changes with time showed that women who smoked during their first pregnancy but refrained from smoking during their subsequent pregnancy had significantly increased birth weight for the second infant, and conversely, infants born to women who initiated smoking with the subsequent pregnancy had significantly decreased birth weight compared to the previous infant. Findings of the study may be used to inform and to guide the development of population focused interventions to decrease maternal prenatal smoking in first and in subsequent pregnancies in an effort to improve infant birth weight outcomes.