出典:国際連合
The mortality of live-born children who have not yet reached their first birthday is called infant mortality 1. The mortality of live-born children who die before reaching a certain age taken as four weeks or 28 days, the so-called neo-natal period 3, is called neo-natal mortality 2. The mortality during the first week of life is called early neo-natal mortality 4. The term post-neonatal mortality 5 refers to deaths after the neo-natal period, but before reaching the age of one year.