Infant Mortality

Infant mortality is a particularly useful measure of health status because it both indicates current health status of the population and predicts the health of the next generation (NCHS, 2001). Infant mortality in the U.S. is defined as the death of an infant before his or her first birthday. It does not include still births. Infant mortality is composed of neonatal (less than 28 days after birth) and postneonatal (28 to 364 days after birth) deaths.

This indicator presents infant mortality for the U.S. based on death certificate data and linked birth and death certificate data recorded in the National Vital Statistics System (NVSS). The NVSS registers virtually all deaths and births nationwide, with data coverage from 1940 to 2013 and from all 50 states and the District of Columbia.

In 2013, a total of 23,446 deaths occurred in children under 1 year of age, 208 fewer deaths than were recorded in 2012 (NCHS, 2015a). Exhibit 1 presents the national trends in infant mortality between 1940 and 2013 for all infant deaths as well as infant deaths by sex, race, and ethnicity. A striking decline has occurred during this time period, with total infant mortality rates dropping from nearly 50 deaths per 1,000 live births in 1940 to under six deaths per 1,000 live births in 2013. Beginning around 1960, the infant mortality rate has decreased or remained generally level each successive year through 2013.

Exhibit 1 presents infant mortality rates in the U.S. by sex and some races (whites and blacks) for the entire period of record, and ethnicity and other races (American Indians or Alaska Natives, Asians or Pacific Islanders) since first reported in 1995. Infant mortality rates per 1,000 live births ranged from 6.8-7.0 from 2000 to 2005, were 6.7-6.8 from 2006-2007, and then decreased or remained steady each year from 2008 (6.6) to 2013 (6.0). Infant mortality rates continue to be highest among males and highest among blacks. The infant mortality rate for blacks decreased from 14.1 per 1,000 live births in 2000 to 11.2 per 1,000 live births in 2013. However, this is still twice the rate compared to white infants, which ranged from 5.7 per 1,000 live births in 2000 to 5.1 per 1,000 live births in 2013.

In 2013, the infant mortality rate was 5.0 per 1,000 live births for Hispanic infants, which is lower than the rate observed in 2012 (5.1). There was a slight increase in the infant mortality rate for non-Hispanic white infants, with 5.0 per 1,000 live births in 2012 compared to 5.1 in 2013. A decrease in the mortality rate was seen for non-Hispanic blacks, with a rate of 11.2 per 1,000 live births in 2012 compared to 11.1 in 2013 (NCHS, 2015a).

Exhibit 2 presents leading causes of infant death in the U.S. for the most recent reporting year. In 2013, the 10 leading causes of infant mortality in the U.S. accounted for about 69 percent of all infant deaths (Exhibit 2), with the subgroup consisting of congenital anomalies (i.e., congenital malformations, deformations, and chromosomal abnormalities) having the highest rate at 1.2 per 1,000 live births (NCHS, 2015a). This category alone accounts for 20 percent of all infant deaths in 2013 (Exhibit 2). In 2013, the top 10 leading causes and their ranks remained the same as those in 2012 except that newborns affected by maternal complications of pregnancy surpassed sudden infant death syndrome to become the third leading cause (CDC, 2015; NCHS, n.d., 2015a).

Congenital anomalies were ranked highest, followed by disorders related to short gestation and low birth weight, among the different racial and ethnic groups except for non-Hispanic blacks. The leading causes of infant mortality among non-Hispanic blacks were short gestation and low birthweight, followed by congenital anomalies. There were small differences in some of the other leading causes of infant mortality between racial and ethnic groups. For example, accidents (unintentional injuries) and placenta cord membranes were the fifth and sixth leading cause of infant death among non-Hispanic white and black infants, respectively; whereas these two causes of infant death were reversed (i.e., placenta cord membranes was fifth and unintentional injuries was sixth) among Hispanic infants (Exhibit 2).

In addition, the Centers for Disease Control and Prevention (CDC) report a substantial difference in the leading causes of death during the neonatal versus the postneonatal periods. Disorders related to short gestation and low birthweight were the leading cause of death for neonates and sudden infant death syndrome was the leading cause of death for postneonates, based on 2013 data (NCHS, 2014). (Data not shown.)

• Cause of death rankings denote the most frequently occurring causes of death among those causes eligible to be ranked. The rankings do not necessarily denote the causes of death of greatest public health importance. Further, rankings of cause-specific death could change depending on the defined list of causes that are considered and, more specifically, the types of categories and subcategories that are used for such rankings (NCHS, 2005).
• Mortality rates are based on the underlying cause of death as entered on a death certificate by a physician. Incorrect coding and low rates of autopsies that confirm the cause of death may occur. Additionally, some individuals may have had competing causes of death. When more than one cause or condition is entered by the physician, the underlying cause is determined by the sequence of conditions on the certificate, provisions of the ICD [International Classification of Diseases], and associated selection rules and modifications (CDC, n.d.). Consequently, some misclassification of reported mortality might occur as a result of these uncertainties, as well as the underreporting of some causes of death.

Infant mortality data for total, males, females, whites, and blacks in Exhibit 1 were obtained from detailed tables published by CDC's National Center for Health Statistics (NCHS, 2015b), which provide annual natality data from 1975 to 2013 and decadal data for 1940, 1950, 1960, and 1970. The total number of infant deaths for each population group (e.g., non-Hispanic black) and the infant mortality data in Exhibit 1 for American Indians or Alaska Natives, Asians or Pacific Islanders, non-Hispanic whites, non-Hispanic blacks, and Hispanics were obtained from Table 5 and Table B/D, respectively, in NCHS’s reports on infant mortality statistics from the period linked birth/infant death data set (NCHS, 2004, 2013, 2015a). Data in the NCHS documentation are based in part on unpublished work tables, available on the NCHS website at http://www.cdc.gov/nchs/deaths.htm. For leading cause of infant death data shown in Exhibit 2, numbers for each of the 10 individual leading causes were extracted from the Linked Birth/Infant Death Records on CDC’s Wide-ranging Online Data for Epidemiologic Research (WONDER) Online Database (CDC, 2015) (http://wonder.cdc.gov/lbd.html). Supporting documentation for leading cause of infant death data came from available NVSS documentation (NCHS, n.d., 2014, 2015a).