Infant Mortality Data Technical Notes
DefinitionsAn infant death is a death within the first year of life. A neonatal death is the death within the first 27 days of life. A postneonatal death is the death of an infant from 28 days to one year of life.
All data in the infant mortality query pertain to live-born infants. A live birth is defined as the complete expulsion or extraction from its mother of a product of conception, irrespective of the duration of pregnancy, which, after such separation, breathes or shows any evidence of life, such as beating of the heart, pulsation of the umbilical cord, or definite movement of voluntary muscles. The vital statistics term for stillbirths is fetal deaths and they are not included in the infant death query. Data for deaths of children one year of age and older are in the Mortality Query.
Sources of Data
Linked Births/Infant DeathsThe death certificate for each infant is linked to his or her birth certificate, when available, by the New Jersey Department of Health's Center for Health Statistics. 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.
Infant DeathsThe death certificate is the source document for the death data included in the linked birth/infant death data set. New Jersey law requires the prompt filing of a death certificate by the proper authority, such as hospital personnel, physicians, medical examiners, and funeral directors, in the event of a death occurring in the state. These certificates are submitted to the office of the State Registrar, where they are recorded and filed permanently.
BirthsThe birth certificate is the source document for data included in the linked birth/ infant death data set. Birth certificate data are also used to calculate infant mortality rates. New Jersey law requires that the attending physician, midwife, or person acting as midwife file a certificate of birth with the Local Registrar within five days of a birth within the state.
Out-of-State Births and DeathsStatistics on births and deaths of New Jersey residents which occurred in other states are obtained through participation in the national Vital Statistics Cooperative Program (VSCP), which encourages the exchange of information on vital events between the states of occurrence and residence. The infant mortality data presented in the query system are for New Jersey residents, regardless of where the death occurred.
Data File UpdatesThe birth and death data in the query system were generated from data files available at the time of preparation of the back-end dataset. Any data pertaining to a birth or death for which a certificate was filed after that time or relating to corrections or revisions made since the data were processed for the electronic file are not included. Vital events computer files are periodically updated by the New Jersey Department of Health's Bureau of Vital Statistics and Registration (BVS) and Center for Health Stastistics (CHS) staff based on correction reports received from local registrars and from data quality control analyses conducted by CHS. The query incorporates data from the most recently updated files.
Quality of DataThe reporting of births and deaths is considered to be essentially complete. According to the National Center for Health Statistics (NCHS), more than 99% of births and deaths are registered. The completeness of reporting by residence is dependent on the effective functioning of the interstate data exchange program for certificates which is fostered and encouraged by NCHS. Research has shown that there is some degree of slippage in receiving information on all vital events of New Jersey residents occurring in other states. However, the number of missing events is thought to be small, relative to the overall number of events.
The quality of the data included in the query is a function of the accuracy and completeness of the information recorded on the respective certificates and of the quality control procedures employed in the coding and keying processes. A query program in which the individual(s) responsible for completing the certificate is questioned about missing or conflicting information is carried out by BVS staff. This process is augmented by the data quality control analyses performed by the CHS using all of the NCHS edit criteria.
In order to participate in the national VSCP, states had to achieve an error rate of 2% or less on each certificate item for three consecutive months. The error rates relate to both coding and data entry errors. New Jersey has met the error tolerance requirements for the cooperative program. After satisfying initial requirements, a monthly sample of records is used to determine that the error rate on each birth certificate item is approximately 4%. Among death certificate items, the error rate is approximately 2% for each death certificate item other than the medical cause of death information. Due to the complexity of the coding system, cause of death coding has a 5% error tolerance level set by NCHS.
NCHS requires states to have an birth/infant death match rate of at least 90%. New Jersey's rate of 93% meets this requirement.
Allocation of Data by Residence or OccurrenceFor public health planning and policy determination, the most useful population to study is usually the resident population of an area. In the case of vital events, the existence of resident certificate exchange agreements among the registration areas in the country permits analysis of resident vital event statistics regardless of where the event occurred. In the query system, the data presented represent infant deaths to New Jersey residents, regardless of where they occurred. Infant deaths that occurred in New Jersey to non-NJ residents are not included.
Allocation of vital events by place of residence within the state is sometimes difficult because classification depends on the statement of the usual place of residence provided by the informant at the time the certificate is completed. For a variety of reasons, the information given may be incorrectly recorded. A common source of error is the confusion of mailing address with residence address. For this reason, all records are run through geocoding software to properly assign the county and municipality of residence.
Race, Ethnicity, and NativityOne race group (White, Black, American Indian/Alaska Native, Chinese, Japanese, Hawaiian, Filipino, Asian Indian, Korean, Samoan, Vietnamese, Guamian, other Asian/Pacific Islander, other race, and an unknown race category) and an ethnicity (Non-Hispanic, Mexican, Puerto Rican, Cuban, Central or South American, other Hispanic, and an unknown ethnicity category) are recorded for each parent of each individual for whom a birth certificate is filed. Race and ethnicity of the child are not recorded and that of the mother is used for statistical analysis. Race and ethnicity can be combined to make a Hispanic "race" group and this is the standard way the New Jersey Department of Health reports vital event data. The race and ethnicity data in the infant mortality query are that of the mother as recorded on the birth certificate, not of the infant as recorded on the death certificate.
Race/ethnicity designations used in the infant mortality query are White, Black, Hispanic, Asian, Native Hawaiian/Other Pacific Islander, American Indian/Alaska Native, and Other Single Race, where Hispanics may be of any race and the other race groups do not include Hispanics (but include those with ethnicity not stated). The Hispanic category includes persons of Mexican, Puerto Rican, Cuban, Central/South American, or other Hispanic ethnicity, regardless of race. The Asian category includes persons of Chinese, Japanese, Filipino, Asian Indian, Korean, Vietnamese, and other Asian descent. The Native Hawaiian/Other Pacific Islander category includes persons of Hawaiian, Samoan, Guamian, and other Pacific Islander descent. The Other Race category includes all race groups other than White, Black, Asian, Native Hawaiian/Pacific Islander, and American Indian/Alaska Native. When combining race and ethnicity, Hispanic ethnicity takes precedence over whatever race is recorded for the mother.
Three nativity categories are used in the query: native-born, Puerto Rico-born, and foreign-born. Native-born includes mothers born in the 50 states or Washington, D.C. Foreign-born includes mothers born anywhere other than the 50 states, D.C., and Puerto Rico. Foreign-born, therefore, includes other U.S. territories such as American Samoa, Guam, and U.S. Virgin Islands because all territories are not coded separately in the electronic birth files. Foreign-born also includes those born abroad to American parents because birth certificates do not have an item to distinguish those cases. Numbers of births to New Jersey residents born in territories other than Puerto Rico or born abroad to American parents are extremely small.
Cause of Death RankingsRankable causes of death in the infant mortality query are based on 71 distinct causes of death derived from the NCHS List of 130 Selected Causes of Infant Death.
New Jersey also uses a list of 10 cause groups and one residual category modified from the 71 Cause List that groups causes of death that rarely occur among New Jersey residents. This list may also be used for ranking causes of death with the caveat that "Other than 10 Major Causes" is not eligible to be ranked.
RatesThe presentation of infant mortality rates facilitates comparisons between geographic areas with populations of different sizes or between subgroups of a population. Infant mortality rates are calculated by dividing the number of deaths of the residents under one year of age of an area or demographic subgroup by the number of births to the residents of the same area or subgroup and are usually expressed per 1,000 births. Infant deaths are limited to those that occur within a specific time period, usually a year, and the birth data used for rate calculation is that of the same year.
In order to compare infant death experiences among various maternal ages and races/ethnicities, infant mortality rates may be computed for subgroups of the population. These are referred to as age- or race/ethnicity-specific rates and are calculated by dividing the number of infant deaths within a subgroup by the births in the subgroup. Death rates from specific causes may also be calculated, with the numerator consisting of the deaths from the particular cause in an area and the denominator comprised of births in the same time period.
The definition of rates used in the query system are on the Definitions of Public Health Terms and Acronyms page . It should be noted that alternative forms exist for some of these statistics. Some other states and the federal government may employ different formulae for the computation of selected rates.