THE PREVALENCE OF MATERNAL SMOKING INTENSITY STATUS IN EARLY AND LATE PREGNANCY AND ITS ASSOCIATION WITH EARLY MORBIDITY IN SINGLETON TERM BIRTHS IN THE UNITED STATES, 2016

Abstract

Relatively little is known about how maternal cigarette smoking influences the health of infants delivered at term. This study was based on the 2016 United States Natality File of live births (N= 3,956,112). The first aim was to examine the prevalence and patterns of smoking in the three months before and during pregnancy and the distribution of smoking intensity in early (1st and 2nd trimester) and late (3rd trimester) pregnancy across race/ethnicity, age, and educational attainment of mothers with all births and with singleton term births (37-41 completed weeks gestation) in the United States in 2016. The second aim was to compare the odds of low birthweight (LBW), low 5-minute Apgar score, and neonatal intensive care unit (NICU) transfer/admission in term singletons with changing maternal smoking status in early and late pregnancy indicating a potential prenatal exposure effect. The third aim was to test and identify the role of low birthweight, as a potential mediator, in the association with maternal smoking status and NICU transfer/admission of a newborn delivered at term. The prevalence of smoking in the three months before pregnancy was 9.42% among all mothers and 9.20% among mothers of term singletons, and high intensity smoking was the highest in the first trimester among non-Hispanic White women, 20-24 years of age, and less educated women for all births and for singleton term births. High intensity smoking in early and late pregnancy was associated with a greater risk of LBW (aOR 3.33; 95% CI: 3.23, 3.44), low 5-min Apgar score (aOR 1.46; 95% CI: 0.88, 2.44), and NICU transfer/admission (aOR 1.62; 95% CI: 1.58, 1.67) in term neonates. The odds ratios of the natural direct and natural indirect effects of NICU transfer/admission were aOR 1.52 (95% CI: 1.47, 1.57) vs. aOR 1.07 (95% CI: 1.07, 1.09) and the proportion mediated through LBW (18.3%) indicated partial mediation. This study has important implications for clinical practice, public health policy and research, and it is particularly timely because of an information gap on the health of infants delivered at term with LBW to mothers who continue smoking at high intensity during pregnancy.