Gestational Age

Definition - What does Gestational Age mean?

Gestational age refers to how far along a pregnancy is. It is a term commonly used throughout pregnancy and immediately after birth to describe the baby's development and the length of the pregnancy. Gestational age is calculated and described in weeks; the average pregnancy ranges between 38-42 weeks long.

Gestational age may also be called fetal age.

FertilitySmarts explains Gestational Age

There are three primary ways gestational age is calculated prior to birth:

  1. First day of last menstrual period.
  2. Day of embryo transfer during in vitro fertilization.
  3. Ultrasound. A fetus becomes measurable on an ultrasound machine 5 to 6 weeks after the mother’s missed period. When completing the exam, measurements of head size, thigh bone and abdomen are considered in order to make a determination on gestational age.

Typically, a combination of these methods are used to determine gestational age and to provide an estimated due date for the baby's birth.

After birth, an infant’s gestational age can be confirmed by utilizing measurements of the following:

  • Weight
  • Length
  • Muscle tone
  • Skin condition
  • Posture
  • Head circumference
  • Reflexes
  • Vital Signs
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