Age Terminology During the Perinatal Period

TermDefinitionUnits of Time
Gestational ageTime elapsed between the first day of the last menstrual period and the day of deliveryCompleted weeks
Chronological ageTime elapsed since birthDays, weeks, months, years
Postmenstrual ageGestational age + chronological ageWeeks
Corrected ageChronological age reduced by the number of weeks born before 40 weeks of gestationWeeks, months