In Reply.
— Sudden infant death syndrome is the sudden death of an infant younger than 1 year that remains unexplained after a complete postmortem investigation, including autopsy, examination of the death scene, and review of the case history. The current registration of vital events in the United States does not include this recent and evolving definition of SIDS. However, the validity of the data presented in our article is strengthened by the high autopsy rate and the distinct age distribution of the infants classified as having died from SIDS. In addition, our study found a striking contrast in the seasonal pattern of SIDS compared with other causes of postneonatal death, such as injuries.The significance of the West-to-East gradient associated with SIDS among white infants remains to be determined. The hypothesis that this gradient may be due to racial misclassification among Hispanics is not supported by analysis of linked