High infant mortality rates are a reflection of poor economic conditions, unmet health care needs, and other unfavorable environmental factors.

Calculated by dividing the number of infant deaths in a calendar year by then number of live births registered for the same time period.
Rates are usually per 1000 or per 100,000 live births.
# deaths in a year of children <1 year of age # live births that same year

Neonatal mortality rates - index of the risk of dying during the first 28 days of life.
# deaths in one year for children <28 days of age
# live births the same year

Post-neonatal mortality rate - index of the risk of death in infants 28 days to 11 months.
#death in one year for children 28 days to 11 months
# live births in the same year