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Maternal cigarette smoking: effect on infant birth weight.

To the Editor.— "A Clinical Trial of Change in Maternal Smoking and its Effect on Birth Weight"1advances the argument that it is indeed smoking during pregnancy that is responsible for the smokers giving birth to lighter babies and not the constitution of the smoker. Yerushalmy2had argued the converse, that the behavioral and constitutional differences between smokers and nonsmokers and not the exogenous effect of smoking per se had accounted for the observed birth-weight differential. However, this study demonstrates how difficult it is, as observed by Goldstein,3to nail the coffin closed on the ghost of Yerushalmy. Although we are not inclined to argue the Yerushalmy case, we do feel there are several ways that the analysis could be improved and the conclusions strengthened. 1. Although birth weight was greater among the treated group, the authors did not demonstrate that decreased smoking itself was responsible; the