Impact of Combined Maternal Alcohol and Tobacco Use on Low Birth Weight in Singleton Pregnancies: A Population Based Study in the U.S., 2003

Background: LBW is defined as Birthweight  < 2500 grams/5.5 pounds or below the 10th percentile for gestational age. LBW is a frequent marker of maternal/infant health and is considered a Leading Health Indicator. Alcohol or tobacco use has been established as an independent risk for LBW with smoking alone accounting for 20-30% of all LBW in the US. Objective: The purpose of this study was to determine the risk for LBW relative to combined maternal alcohol and tobacco use, and to explore their role in contributing to the Black-White disparity within the framework of the weathering hypothesis. Although a national problem, LBW is not evenly distributed throughout the population. Black women consistently are twice as likely to have a LBW infant than non-black mothers. Geronimus introduced the theoretical framework of the weathering hypothesis two decades ago to explore this inequality. Weathering is a concept of explaining women's health as a process over time that reflects insults and injuries from conception to the current. It is indicative of her life experiences that either promote or retard health. Stressors, many chronic in nature, exert a cumulative influence and may accelerate the weathering process. Data Set: Approximately 4 million birth certificates comprise the natality files produced by the National Center for Health Statistics. Results: Overall, women living in cities with a population of 500,000-1 million had the highest percent of reported drinking. Women living in cities of 250,000-500,000 had the highest incidence of smoking. The incidence of LBW in the Black non-Hispanic group was repeatedly twice that of their White counter parts (12% versus 5%). Black women experienced childbearing 5 years earlier, were not married, smoked less, and lived in large metropolitan counties of >1 million in comparison to the White women. The highest incidence of LBW in the Black group was in the age group of 45-49 years while the White group was in the age group of <15 years. The rate of LBW rose sharply with the Black maternal age, but not with the White maternal age, supporting the weathering hypothesis. Black non-Hispanic women who were both tobacco and alcohol users were 3.2 times more likely to have a LBW neonate and White non-Hispanic women were 2.9 times more likely to have a LBW neonate than non-users. Despite the increased odds for having a LBW infant with concomitant substance abuse of tobacco and alcohol, the rate in the Black women was 2.2 times more than the White women. This risk taking behavior clearly increases the incidence of LBW, but affects both races in a similar fashion and thus the relative risk of combined tobacco and alcohol use does not account for the discordant rate of LBW in the Black population. Summary: LBW inequality in the United States continues to plague the perinatal environment. Although no one variable has been demonstrated to have a singular causal relationship, the research must continue to explore all possible risk factors for LBW.