The age of the fetus measured from the date of conception. In the past, it has been estimated from the first day of the last normal menstrual period before the beginning of pregnancy. Ultrasound allows a more precise estimate. It is expressed in completed days or weeks of pregnancy. Variations of gestational age include preterm (less than 37 weeks or 259 days), term (37–42 weeks or 259–293 days), and postterm (42 weeks or 294 days, or more).
Subjects: Public Health and Epidemiology.