To the Editor.
—We appreciate Drs Cohn and Klein's interest in our study and regret any confusion they had regarding our definitions of rural and urban. Our definitions were established by North Carolina's Department of Environment, Health, and Natural Resources when it initiated the Survey of Childbearing Women in late 1988. As stated in our article, the 10 most populous counties, in which populations range from 100 000 to 520000, were designated as urban and the remaining 90 North Carolina counties were designated rural. While it is true that this classification does not correspond to the Census definition of rural or the OMB definition of nonmetropolitan, all such definitions have a degree of arbitrariness in them and were not designed as epidemiologic descriptors. For instance, it is difficult for us to consider Madison County, population 16 953 (largest town, 1600), or Davie County, population 27 859 (largest town, 3400), as metropolitan, but they