The neonatal period, the first 4 weeks of life after birth represents a time of rapid change for newborns. Too often, the first 28 days of life after birth represent the most vulnerable time for a child’s survival. According to the World Health Organization (WHO), "in 2015, 2.7 million deaths, or roughly 45% of all under-five deaths, occur during this period. Of these, almost 1 million neonatal deaths occur on the day of birth, and close to 2 million die in the first week of life. The proportion of child deaths which occur in the neonatal period has increased in all WHO regions over the last 25 years." Learn more about some of the main changes that occur during a newborn's first month of life here.