The classification of heat-related deaths solely according to body temperatures underestimates the magnitude of heat-related mortality during heat waves. Broader classifications are often used, but their utility in defining the mortality and identifying at-risk populations has not been evaluated. Using death data from the July 1995 heat wave in Chicago, the authors compared heat-related mortality rates based on the classification of heat-related deaths by the Cook County Medical Examiner's Office (CCMEO), with excess mortality rates based on total mortality differentials during and before the heat wave. In July 1995, the overall mortality in Chicago was 19 deaths per 100,000 population for heat-related mortality and 24 to 26 deaths per 100,000 population for excess mortality. Across Chicago community areas, the two mortality rates were closely related (r = 0.73-0.79; p < .01), but heat-related mortality rates were lower than excess mortality rates in community areas where excess mortality rates were higher (slope < 1; p < .01), a finding indicating an underestimation of heat-related deaths in such areas. The underestimation could not be explained by uncertainties in estimating excess mortality rates or by differences in socioeconomic and demographic characteristics among communities. These results support using the broader CCMEO classification of heat-related deaths as a relative indicator to target communities for prevention and relief efforts, but not as an adequate measure of actual heat-related mortality in a high-risk neighborhood.

Although numerous infants have been reported with transverse limb deficiencies after their mothers had undergone chorionic villus sampling (CVS), it has been unclear whether the procedure caused these defects. We report the results of the first multistate case-control study to assess and quantify the risk for specific limb deficiencies associated with CVS. Case subjects were 131 infants with nonsyndromic limb deficiency ascertained from 7 population-based birth defect surveillance programs, and born from 1988-1992 to mothers 34 years of age or older. Control subjects were 131 infants with other birth defects. We ascertained exposure to CVS from medical records and maternal and physician questionnaires. We assessed rates and timing of exposure to CVS, and estimated relative and absolute risks for anatomic subtypes of limb deficiency. The odds ratio for all types of limb deficiency after CVS from 8-12 weeks' gestation was 1.7 (95% confidence interval, 0.4-6.3). For specific anatomic subtypes, the strongest association was for transverse digital deficiency (odds ratio = 6.4; 95% confidence interval, 1.1-38.6). The risk for transverse digital deficiency increased with earlier gestational exposure (P < 0.01 for trend). We estimated that the absolute risk for transverse digital deficiency in infants after CVS was 1 per 2,900 births (0.03%). Exposure to CVS was associated with a sixfold increase in risk for transverse digital deficiency. The causality of this association is supported by its strength, specificity, biologic plausibility, and consistency with the results of previous studies. Although some centers already inform patients about risk for limb deficiency, this study quantifies the magnitude of risk associated with CVS from 8-12 weeks' gestation.

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