Skip directly to searchSkip directly to the site navigationSkip directly to the page's main content

Infant Mortality Data Technical Notes

Click a bar to expand or collapse its content.

An 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.

Linked Births/Infant Deaths

The 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 (CHS). 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 Deaths

The 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 Vital Statistics and Registry (OVSR), where they are recorded and filed permanently.


The birth certificate is the source document for prenatal, birth, and immediate postnatal 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 Deaths

Statistics 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 Updates

The 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 OVSR and 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.
The 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 in the respective electronic systems 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 OVSR staff. This process is augmented by the data quality control analyses performed by CHS using all of the NCHS edit criteria.

NCHS's goal is for states to have an infant death/birth certificate match rate of 100%. New Jersey's rate in 2017 was 99.5%.
For 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 nativity used in the Infant Mortality Query are that of the mother as reported on the infant's birth record.
Rankable 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.
The 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.
Caution should be exercised in the interpretation of rates based on small numbers. Chance variations in the number of infant deaths occurring in sparsely populated areas can cause rates to fluctuate widely over time. In accordance with NCHS standards, rates based on fewer than 20 infant deaths or fewer than 20 births in the denominator are considered unreliable for analysis purposes. Therefore, these rates are not displayed and are indicated by ** in the appropriate cell. For purposes of analyzing infant mortality rates for small areas, calculation of three- or five-year average rates and other statistical methodologies for analyzing small numbers may provide more meaningful measures.
The information provided above is from the Department of Health's NJSHAD web site ( The information published on this website may be reproduced without permission. Please use the following citation: " Retrieved Sat, 18 May 2024 16:46:40 from Department of Health, New Jersey State Health Assessment Data Web site: ".

Content updated: no date