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Clinical Obstetrics

Poster Session 2

(400) Association of Trimester-Specific Smoking Cessation and Risk of Stillbirth

Tuesday, February 13, 2024
3:30 PM – 5:00 PM  
Location: Prince George's Exhibit Hall CDE, Lower Atrium Level

    Primary & Presenting Author(s)

  • Morgan Buckley, BS

    Medical Student
    University of Cincinnati College of Medicine
    Cincinnati, OH, United States

    • Coauthor(s)

  • RR

    Robert M. Rossi, MD

    Assistant Professor
    University of Cincinnati College of Medicine
    Cincinnati, OH, United States

  • Emily A. DeFranco, DO, MS

    Professor
    University of Cincinnati College of Medicine
    Cincinnati, OH, United States

Objective: Tobacco use in pregnancy is associated with stillbirth and other adverse pregnancy outcomes. This study aims to quantify the relative influence of smoking cessation at various timepoints in pregnancy on stillbirth risk.  

Study Design: Population-based retrospective cohort study of all US live births and stillbirths using vital statistics birth records, 2014-2019. Outcomes of women who reported smoking only in the 3 months prior to conception, through first trimester then quit, through second trimester then quit, and smoked throughout pregnancy were compared to a referent group of nonsmokers. Generalized linear modeling estimated the relative risk of smoking duration during pregnancy on stillbirth risk and was also stratified by categories of number of cigarettes smoked per day. Outcomes were limited to births at 32-42 weeks. 

Results:

Of 23,500,558 births, 10.0% smoked either preconception only or anytime during the pregnancy. The overall stillbirth rate during the study period was 0.26%, 0.20% in non-smokers, and 0.29% in smokers. Stillbirth rate was 0.20% among preconception only smokers, 0.26% and 0.31% when smoking cessation occurred after the first or second trimester, respectively, and the highest among those who smoked throughout pregnancy 0.34%, p < 0.0001.  Smoking limited to preconception only had no significant association with stillbirth, however stillbirth risk demonstrated a sequential increase with longer durations of smoking during pregnancy, with highest risk among those who smoked throughout pregnancy. Stillbirth risk was also higher among those who smoked higher number of cigarettes per day (figure).  

Conclusion: Smoking during pregnancy is associated with increased risk of stillbirth, with sequential increased risk with longer durations of smoking during pregnancy and smoking a higher number of cigarettes per day. These data demonstrate that quitting earlier in pregnancy is optimal, and for those who do not quit, smoking fewer number of cigarettes per day may help to minimize the risk of stillbirth.