Living Reference Work Entry

Encyclopedia of Behavioral Medicine

pp 1-2

Date: Latest Version

Birth Weight

  • Linda C. BaumannAffiliated withSchool of Nursing, University of Wisconsin-Madison Email author 
  • , Alyssa YlinenAffiliated withAllina Health System Email author 


Low birth weight; Full term newborn


The birth weight of a newborn is an indicator of chance for survival and long-term development and can also reflect the health status of the birth mother. Normal birth weight is classified as babies born between the 10th and 90th percentiles of all babies of the same gestational age. Low birth weight is a major problem of newborns worldwide. There are three categories of low birth weight: low birth weight (LBW) is less than 2,500 g or about 5.5 lb; very low birth weight (VLBW) is less than 1,500 g; and extremely low birth weight (ELBW) is less than 1,000 g. Low-birth-weight infants are either born small for their gestational age (SGA) or born prematurely. A preterm birth is a gestation of less than 37 weeks and is a major cause of LBW. Small for gestational age births are more common in developing countries.

High birth weight is far less common worldwide but can still have major consequences on the health of both the mother and the in ...

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