Infant mortality rate (IMR) is the number of deaths of infants under one year of age per 1,000 live births. It is an important indicator of the overall health of a society, reflecting the social, economic, and environmental conditions in which children live, including their access to healthcare. The IMR is calculated by dividing the number of children dying under one year of age by the number of live births during the year, multiplied by 1,000.

There are different forms of infant mortality, including perinatal mortality, which is the death of a fetus after 22 weeks of gestation or the death of a newborn up to one week postpartum, and neonatal mortality, which is death occurring within 28 days postpartum. Neonatal death is often attributed to inadequate access to basic medical care during pregnancy and after delivery, and it accounts for 40–60% of infant mortality in developing countries.

The IMR varies among countries and population groups. In 2021, the infant mortality rate in the United States was 5.4 deaths per 1,000 live births. The continent of Africa has the highest infant mortality rate of any region studied, with 68 deaths per 1,000 live births. The IMR is not only a statistic but also a reflection of socioeconomic development, as such it effectively represents the presence of medical services in a country.

The IMR is an effective resource for health departments making decisions on medical resource allocation, and also formulates global health strategies and helps identify vulnerable populations. The IMR is considered a primary and important indicator of a geographic area’s overall health status or quality of life. However, there are concerns about the quality of reporting of infant mortality internationally and within states, especially in terms of defining a live birth and/or complete reporting of both birth and death certificates for very low birth weight babies.