DefinitionGestation is the period of time between conception and birth during which the fetus grows and develops inside the mother's womb.Gestational age is the time measured from the first day of the woman's last menstrual cycle to the current date. It is measured in weeks. A normal pregnancy can range from 38 to 42 weeks.Infants born before 37 weeks are considered premature. Infants born after 42 weeks are considered postmature. The gestational maturity rating is measured after the baby is born by the Ballard scale or Dubowitz exam.Alternative NamesFetal age; GestationInformationGestational age can be determined before or when the baby is born.Prior to birth, growth is determined with ultrasound by measuring the size of the head, abdomen, and thigh bone.Following birth, assessing an infa