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The first weight of the fetus or baby obtained after birth. The World Health Organization further defines the following categories:

  • extremely low birthweight: less than 1,000 grams (up to and including 999 grams),
  • very low birthweight: less than 1,500 grams (up to and including 1,499 grams),
  • low birthweight: less than 2,500 grams (up to and including 2,499 grams).




International Classification of Diseases and Related Health Problems, 10th Revision, WHO, 1992

The definitions of low, very low, and extremely low birthweight do not constitute mutually exclusive categories. Below the set limits they are all-inclusive and therefore overlap (i.e. low includes very low and extremely low, while very low includes extremely low).

For live births, birthweight should preferably be measured within the first hour of life before significant postnatal weight loss has occurred. While statistical tabulations include 500 gram groupings for birthweight, weights should not be recorded in those groupings. The actual weight should be recorded to the degree of accuracy to which it is measured.


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