National Vital Statistics System

Linked Birth and Infant Death Data

The linked birth and infant death data set is a valuable tool for monitoring and exploring the complex inter-relationships between infant death and risk factors present at birth. In the linked birth and infant death data set the information from the death certificate is linked to the information from the birth certificate for each infant under 1 year of age who dies in the United States, Puerto Rico, The Virgin Islands, and Guam. The purpose of the linkage is to use the many additional variables available from the birth certificate to conduct more detailed analyses of infant mortality patterns. The linked files include information from the birth certificate such as age, race, and Hispanic origin of the parents, birth weight, period of gestation, plurality, prenatal care usage, maternal education, live birth order, marital status, and maternal smoking, linked to information from the death certificate such as age at death and underlying and multiple cause of death.




Data Collection


Data Processing




Downloadable Data Sets are Available in Two Different Formats

The linked birth and infant death data set is available in two different formats: period data and birth cohort data. The numerator for the period linked file consists of all infant deaths occurring in a given data year linked to their corresponding birth certificates, whether the birth occurred in that year or the previous year. The numerator for the birth cohort linked file consists of deaths to infants born in a given year. In both cases, the denominator is all births occurring in the year.

The release of linked file data in two different formats allows NCHS to meet customer demands for more timely linked files while still meeting the needs of data users who prefer the birth cohort format. While the birth cohort format has methodological advantages, it creates substantial delays in data availability, since it is necessary to wait until the close of the following data year to include all infant deaths to the birth cohort. The birth cohort files include the denominator-plus file which contains some of the mortality file data at the end of the birth record. Period linked files are currently available for the 1995-2017 data years. Birth cohort linked files are currently available for the 1983-91, and 1995-2013 data years. Linked files were not produced for the 1992-94 data years. Beginning with 1995 data, the period linked file is the basis for all official NCHS linked file statistics.