Maternal cigarette smoking cessation and infant term low birth weight

BACKGROUND AND AIM: Smoking cessation during pregnancy is hypothesized to improve birth outcomes. However, the effect of the cessation time on birth weight among full-term infants merits further attention. We aimed to examine the association of maternal trimester-specific smoking cessation with term low birth weight (TLBW, 2500g). METHODS: We included 183,099 singleton, non-anomalous live births of 37-42 weeks gestation in Western New York between 2004-2018. Based on the self-reported average cigarettes per day during three months before pregnancy and during each trimester, we categorized pregnant women into six mutually exclusive groups: non-smokers; those who quit during the 1st, 2nd, or 3rd trimester; those who smoked throughout pregnancy; and inconsistent smokers. We examined the association between smoking cessation categories and TLBW using logistic regression, adjusting for potential confounders. We further explored the joint effect of smoking and illegal drug use during pregnancy on TLBW. RESULTS:Overall, 13.7% of pregnant women smoked throughout pregnancy; 3.4%, 1.8%, and 0.7% reported quitting smoking during the 1st, 2nd, or 3rd trimester, respectively. Compared to non-smokers, cessation during the 3rd trimester and smoking throughout pregnancy were associated with 1.73 (95% CI: 1.25, 2.39) and 2.28 (95% CI: 2.09, 2.49) times higher odds of TLBW, respectively. The associations were more pronounced for heavy smokers (≥10 cigarettes/day) than light smokers (1-9 cigarettes/day). Quitting smoking during the 1st trimester (OR=0.88, 95% CI: 0.71, 1.09), 2nd trimester (OR=1.22, 95% CI: 0.96, 1.56), or inconsistent smoking (OR=1.28, 95% CI: 0.71, 2.32) was not associated with TLBW. Infants of mothers who smoked throughout pregnancy and used illegal drugs had 2.84 (95% CI: 2.47, 3.25) times higher odds of TLBW compared to non-smokers without illegal drug use. CONCLUSIONS:Delayed smoking cessation, smoking throughout pregnancy, and the combination of smoking and illegal drug use were associated with an increased risk of TLBW. KEYWORDS: Cigarette smoking, Birth weight, Full-term infants, Illegal drug use