Infant Mortality

Definitions

Various measures of infant loss rely on two events: the birth of the child and death before a certain age. As seen in Table 1, infant mortality is defined as the proportion of infants, born alive, who die before their first birthday. Infant mortality can be further divided into neonatal mortality, the deaths of infants in the first month of life, and those dying later in the first year or postneonatal mortality. Whereas death and the age at death are generally readily identifiable events, application of the definition of live birth may be unreliable, especially when the infant dies shortly after birth or is very immature. Examination of all births, those dying before delivery and very early neonatal deaths (perinatal mortality), may be important to assess the effect of different definitions of live birth.

Factors influencing the utility of information on infant mortality rates include the completeness of registration of vital events and the quality of information in the vital records. In most countries, births and infant deaths are recorded as part of the vital statistics systems, which may vary in organization. In many countries, completeness of coverage of vital events cannot be assumed; unregistered births range from 2% in industrialized countries to 71% in the least industrialized countries. Even if deaths are recorded, cause of death information may be lacking, thus hampering interpretation of health events leading to death. Equally important as recording the events themselves is the use of standard definitions and codes for events (e.g., cause of deaths) to enhance comparability of data across sites and time. That, in turn, requires an educated registration workforce that may not be readily available in many areas of the world.

In the United States, data for the various measures of infant mortality come from three separate records: the birth certificate, the death certificate, and the fetal death certificate. The birth certificate has a wealth of information on sociodemographic characteristics, prior obstetric history, prenatal care and complications, complications of delivery, and characteristics of the infant (such as birth weight and gestational age) in the confidential section. In contrast, the death certificate has relatively sparse data focusing on aspects of the place and reason for death with relatively limited sociodemographic and other data. The fetal death record has a bit more information on the pregnancy but not the wealth of information that the birth certificate provides.

...