Smoking during pregnancy is responsible for one in five cases of sudden infant death syndrome (SIDS), a new analysis shows. Among mothers who smoke during pregnancy, smoking is responsible for nearly two out of every three SIDS cases.
In fact, "maternal smoking during pregnancy appears to be the primary modifiable risk factor for SIDS," the research team maintains in their report, published in the October issue of the American Journal of Public Health.
Dr. Kevin Sullivan, from the Rollins School of Public Health of Emory University in Atlanta, and colleagues linked birth and death certificate data obtained from the Georgia State Division of Public Health for the period from January 1997 to December 2000.
Records of 489,494 births included information about the mother's smoking. Nine percent of mothers reported smoking, and the number of SIDS cases totalled 438. The rate of SIDS among infants born to mothers who smoked was 2.4/1000, versus 0.8 per 1000 among nonsmokers.
However, previous studies have also established that maternal smoking as documented on birth records is underreported and substantially misclassified, Dr. Sullivan and his associates point out.
Using a "capture-recapture method" to increase accuracy, the researchers estimate that the proportion of women who smoked while pregnant was 16.5%. They used this figure as the "true" incidence of maternal smoking, and controlled for significant confounders -- gestational age, low birthweight, parity, maternal education, infant gender and maternal status -- to find that the overalll odds ratio was 2.6 for SIDS associated with maternal smoking.
Dr. Sullivan's group estimates that "20.7% of SIDS cases could have been prevented if women had not smoking during pregnancy." Among maternal smokers, they add, 61.3% of SIDS cases were a result of smoking.
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