Online Program

Timing of Smoking During Pregnancy and the Risk of Preterm Birth

Monday, November 2, 2015 : 11:30 a.m. - 11:45 a.m.

Anthony Kondracki, MD, MPH, CPH, Department of Family Science, University of Maryland, School of Public Health, College Park, MD
Sandra Hofferth, PhD, Department of Family Science, University of Maryland, College Park, College Park, MD
background:  Relative to term births, preterm births are associated with an increased risk of mortality.  Smoking during pregnancy has been shown to be linked to a higher rate of preterm birth.  Although there has been a decline in smoking rates among pregnant women, surveillance of the risks of maternal smoking linked to the high rate of preterm birth in the U.S.  is still needed.

objectives:  The present study examines two research questions:  1) is not smoking at all in pregnancy associated with a lower risk of preterm birth than smoking solely in the first trimester? 2) Is smoking continuously throughout pregnancy or smoking only in the first two trimesters associated with an increased risk of preterm birth compared with smoking in the first trimester?

methods: A sample of 1 million births was randomly drawn from the 2008 NCHS Cohort Linked Birth Data Set file, representing singleton births registered in the 50 States and DC.  Logistic regression analysis estimated odds ratios and 95% confidence intervals.

results:  Mothers who did not smoke had a lower risk of preterm birth (OR 0.898 95% CI (0.835, 0.966)) and mothers who smoked in the first and second trimesters had a higher risk of preterm birth than mothers who smoked only in the first trimester (OR 1.708 95% CI (1.507, 1.935)).  

conclusion:  Smoking in the first trimester leads to a greater risk of preterm birth than not smoking.  Smoking in both the first and second trimesters increases the risk substantially, whereas smoking after that does not.

Learning Areas:

Public health or related research

Learning Objectives:
Describe the risk of preterm birth associated with smoking and pregnancy Differentiate risks associated with smoking during a particular trimester of pregnancy Explain maternal characteristics linked to smoking during pregnancy

Keyword(s): Maternal and Child Health, MCH Epidemiology

Presenting author's disclosure statement:

Qualified on the content I am responsible for because: I have been investigating the risk of smoking in pregnancy and preterm birth during my doctoral studies at the University of Maryland, School of Public Health. My research interests include preterm birth and adverse pregnancy outcomes.
Any relevant financial relationships? No

I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.