In 2022, the state of Mississippi had the highest infant mortality rate in the United States, with around 9.11 deaths per 1,000 live births. Infant mortality is the death of an infant before the age of one. The countries with the lowest infant mortality rates worldwide are Slovenia, Singapore, and Iceland. The countries with the highest infant mortality rates include Afghanistan, Somalia, and the Central African Republic. Causes of infant mortality Rates and causes of infant mortality are different depending on the country and region. However, the leading causes of neonatal deaths include preterm birth complications, intrapartum-related events, and sepsis. The leading causes of death among children aged 1 to 59 months are pneumonia, diarrhea, and injury. In the United States The infant mortality rate in the United States has decreased over the past few decades, reaching a low of 5.4 deaths per 1,000 live births in 2021. The most common causes of infant death in the United States are congenital malformations, low birth weight, and sudden infant death syndrome. In 2022, congenital malformations accounted for around 108 infant deaths per 100,000 live births.