Age Stages Defined According to NICHD Pediatric Terminology

StageDefinitions (Release Date July 6, 2011)
Preterm neonatalThe period at birth when a newborn is born before the full gestational period
Term neonatalBirth– 27 d
Infancy28 d–12 mo
Toddler13 mo–2 y
Early childhood2–5 y
Middle childhood6–11 y
Early adolescence12–18 y
Late adolescence19–21 y
  • NICHD, Eunice Kennedy Shriver National Institute of Child Health and Human Development.