Maternal smoking during pregnancy: no association with congenital malformations in Missouri 1980-83.

Using a multisource birth defects registry developed by the Missouri Center for Health Statistics for the years 1980-83, we examined the relation between maternal smoking during pregnancy and the occurrence of congenital malformations. There were 288,067 live singleton births in this data set of which 10,223 had one or more congenital malformations. When adjusted for potential confounders the odds ratio for congenital malformations in the infants of women who smoked during pregnancy was not increased (odds ratio = 0.98, 95% confidence interval = 0.94 - 1.03). We examined the relation between smoking and groups of malformations using the International Classification of Diseases, 9th Revision, as well as analyzing for certain specific malformations within each group and found no increased risk for infants of smokers.