Homo sapiens newborn infant A newborn infant, or neonate, is a child under 28 days of age. NCI: C16731 NCI: C16731 WHO (http://www.who.int/topics/infant_newborn/en/) YL https://ncit.nci.nih.gov/ncitbrowser/ConceptReport.jsp?dictionary=NCI_Thesaurus&version=15.12d&ns=NCI_Thesaurus&code=C16731