Infant mortality refers to the death of infants in the first year of their life. It is measured by the infant mortality rate (IMR), which is the ratio of the total number of deaths to the number of children under the age of one year for every 1,000 live births. IMR is often broken down into three components based on time of death. First, the perinatal mortality rate measures the ratio of the number of late-fetal deaths (at or after 28 weeks gestation) and deaths within the first 7 days after birth per 1,000 live births. Second, the neonatal mortality rate refers to the ratio of the number of deaths within 28 days after birth (per 1,000 live births). Third, the postneonatal mortality rate is ...