Infant mortality is the death of young children under the age of 1.[1] This death toll is measured by the infant mortality rate (IMR), which is the probability of deaths of children under one year of age per 1000 live births.[2] The under-five mortality rate, which is referred to as the child mortality rate, is also an important statistic, considering the infant mortality rate focuses only on children under one year of age.[3]

In 2013, the leading cause of infant mortality in the United States was birth defects.[4] Other leading causes of infant mortality include birth asphyxia, pneumonia, congenital malformations, term birth complications such as abnormal presentation of the fetus umbilical cord prolapse, or prolonged labor,[5] neonatal infection, diarrhea, malaria, measles and malnutrition.[6] One of the most common preventable causes of infant mortality is smoking during pregnancy.[7] Lack of prenatal care, alcohol consumption during pregnancy, and drug use also cause complications which may result in infant mortality.[8][failed verification] Many environmental factors contribute to infant mortality, such as the mother's level of education, environmental conditions, and political and medical infrastructure.[9] Improving sanitation, access to clean drinking water, immunization against infectious diseases, and other public health measures can help reduce high rates of infant mortality.

In 1990, 8.8 million infants younger than 1 year died globally.[10] Until 2015, this number has almost halved to 4.6 million infant deaths.[11] Over the same period, the infant mortality rate declined from 65 deaths per 1,000 live births to 29 deaths per 1,000.[12] Globally, 5.4 million children died before their fifth birthday in 2017.[13] In 1990, the number of child deaths was 12.6 million.[11] More than 60% of these deaths are seen as being avoidable with low-cost measures such as continuous breast-feeding, vaccinations and improved nutrition.[14]

The child mortality rate, but not the infant mortality rate, was an indicator used to monitor progress towards the Fourth Goal of the Millennium Development Goals of the United Nations for the year 2015. A reduction of the child mortality is now a target in the Sustainable Development Goals--Goal Number 3: Ensure healthy lives and promote well-being for all at all ages.[15] Throughout the world, infant mortality rate (IMR) fluctuates drastically, and according to Biotechnology and Health Sciences, education and life expectancy in the country is the leading indicator of IMR.[16] This study was conducted across 135 countries over the course of 11 years, with the continent of Africa having the highest infant mortality rate of any region studied with 68 deaths per 1,000 live births.[16]