Assigning size is a way to measure and monitor the growth of the infant throughout the pregnancy, as well as at the time of birth.
The measurement is based on the estimated gestational age (how many weeks the mother was pregnant) compared to what is considered normal height, weight, head size, and developmental level for a child of the same gestational age and gender.
Graphs are available showing the upper and lower normal limits for different gestational ages, from around 25 weeks of gestation through 42 weeks.
An appropriate for gestational age full-term infant is heavier than 2,500 grams (about 5.5 lbs.) and lighter than 4,000 grams (about 8.75 lbs.).
Knowing the group into which an infant fits is important. An AGA baby tends to have the lowest risk for any problems. AGA babies have lower rates of disease and death than babies that are small or large for their gestational age.