Birth records for all infants with birthweights <750 g born in Ohio during January 1–June 30, 2006, were identified and matched with death records registered through December 31, 2006, using the Ohio Department of Health's vital statistics database. The birth hospitals of infants with only birth records were contacted by telephone to verify discharge status (i.e., alive to home, alive transferred,
or deceased). Deaths among infants that were confirmed (via medical-record review) by the birth hospitals but for which no death records were found were considered unregistered deaths. Selected characteristics of extremely low birthweight infants with unregistered deaths (e.g.,
birthweight, race, and Medicaid coverage) were compared with those with registered deaths using data from birth records. Categorical variables were analyzed using Fisher's exact test, and continuous variables were analyzed using the Wilcoxon rank sum test.