Small for gestational age (SGA) is a term used to describe a baby who is smaller than the usual amount for the number of weeks of pregnancy.

SGA babies may appear physically and neurologically mature but are smaller than other babies of the same gestational age. SGA babies may be proportionately small (equally small all over) or they may be of normal length and size but have lower weight and body mass. SGA babies may be premature (born before 37 weeks of pregnancy), full term (37 to 41 weeks), or post term (after 42 weeks of pregnancy).


  • Small for gestational age (SGA) is below the 10th percentile birthweight after birth.
  • Intrauterine growth restriction (IUGR) is diagnosed in a fetus while still inside the uterus.
  • Low birth weight (LBW) is defined as an infant with a birth weight of less than 2500 g (5 lb 8 oz), regardless of gestational age at the time of birth.
  • Very Low Birth Weight (VLBW) is less than 1500 g, and Extremely Low Birth Weight (ELBW) is less than 1000 g.
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