Infant Mortality Rates
Infant mortality rates are calculated as the number of deaths in the first year of life divided by the number of live births, multiplied by 1000. For the years 1990-1994, the numerator is calculated using data from the Final Mortality File from NCHS, and the denominator is calculated using data from the Natality File. For the years after 1994, the numerator is calculated using data from the Period Linked Birth/Infant Death File, and the denominator is calculated using the Live Birth Denominator File that accompanies the numerator file. The period linked birth/infant death file links information from the birth certificate for each infant under 1 year of age who died in the 50 States, the District of Columbia, Puerto Rico, the Virgin Islands, or Guam and allows more detailed analysis of infant mortality patterns. This file was not prepared by NCHS for the years 1990-1994.
Age at Infant Death
Age at infant death rates include calculations for two age-specific categories: neonatal deaths and postneonatal deaths. The neonatal death rate is calculated as the number of infant deaths that occur between 0-27 days of life (often referred to as the 1st month of life) divided by the number of live births, multiplied by 1000. The postneonatal death rate is calculated as the number of infant deaths that occur from 28 days to under 1 year of life, divided by the number of live births, multiplied by 1000.
Cause of Infant Death
Cause of Infant Death rates are calculated using the Period Linked Birth/Infant Death File for the following causes of death: birth defects, prematurity/low birthweight, sudden infant death syndrome, respiratory distress syndrome, maternal complications of pregnancy, and neural tube defects. Rates are calculated as the number of cause-specific infant deaths divided by the number of live births, multiplied by 100,000.
All causes of death are based solely on the underlying cause of death and compiled in accordance with the International Statistical Classifications of Diseases and Related Health Problems - Ninth Revision (ICD-9) for 1995 through 1998, and Tenth Revision (ICD-10) beginning in 1999. When comparing data between these time periods, it is important to consider the potential impact on coding and definitions of cause of death categories that may have occurred upon transitioning from ICD-9 to ICD-10. To compensate for these discontinuities, NCHS has published cause-specific comparability ratios that when applied more clearly represent trends in mortality statistics from 1998 to 1999. Comparability ratios have not been applied in PeriStats.
|Cause of Death
||Sudden infant death syndrome
||Respiratory distress syndrome
||Maternal complications of pregnancy
Deaths due to neural tube defects include anencephalus, craniorachischisis, iniencephaly, spina bifida with and without hydrocephalus and encephalocele.