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APHA Scientific Session and Event Listing

Ms Puza Pabna Sharma, MD, MPH, Epidemiology, UMDNJ School of public health, 683 Hoes Lane west, P O Box 9, Piscataway, NJ 08854, 813-382-6227, drpuja_s@yahoo.com, Hamisu M. Salihu, MD, PhD, Obstetrics and Gynecology and Reproductive Sciences, UMDNJ Robert Wood Johnson Medical School, 125 Paterson St, New Brunswick, NJ 08901, and Russell Kirby, PhD, Maternal and Child Health, University of Alabama at Birmingham, RPHB 320, 1530 3rd Av S, Birmingham, AL 35294-0022.

Title: Estimating smoking-related stillbirth risk using a case-control and a case-crossover study design

Background: Prenatal smoking has been incriminated as a risk factor for fetal morbidity and mortality mainly in cross-sectional studies. In this study, we sought to estimate the association between prenatal smoking and stillbirth in a longitudinal cohort using two study designs: (1) case-control study and (2) bidirectional case-crossover study.

Methods: Missouri maternally-linked cohort dataset from 1978 through 1997 was used. In the case-control study, each mother contributed only one birth to the analysis. For the bidirectional cross-over design, cases were restricted to women who gave birth to at least one stillbirth; controls comprised all live births before and after the stillbirth. The independent association between prenatal smoking and stillbirth was computed using non-conditional and conditional logistic regression.

Results: Prenatal smoking decreased from 29.7% in 1978 to 21.2% by 1997 (p <0.001). The absolute risk of stillbirth was greater among smokers (7.7/1000) than non-smokers (5.3/1000) [p<0.001]. In the case-control design, the risk of stillbirth among smokers was 34% greater than for non-smokers (OR = 1.34; 95% CI = 1.26-1.43). For each 10 unit increase in the number of cigarettes consumed prenatally, the likelihood of stillbirth rose by about 14% (p < 0.001). In the bi-directional case-crossover design, the association between stillbirth and smoking during pregnancy was confirmed although the magnitude of the relationship was smaller (OR = 1.12; 95% CI = 1.03-1.39).

Conclusions: Prenatal smoking is a precursor of stillbirth as supported by both study designs.

Learning Objectives:

• At the end of the session, participants will be able to
• 1. Conduct retrospective studies that incorporate a hybrid design (case-control and case-crossover) where data is longitudinally gathered.
• 2. Learn how the independent association between prenatal smoking and stillbirth can be measured in case-crossover studies within a population-based study framework.
• 3. Gain knowledge about the significant contribution of prenatal smoking as precursor of stillbirth, and the importance of reinforcing current efforts to prevent smoking during pregnancy.

Presenting author's disclosure statement:

Any relevant financial relationships? No