Birth weight (BWT) is coded in grams. No edit check comparing the birth weight to the diagnosis or procedure codes is performed.

In 1993, Colorado began collecting birth weight of newborns, but it was optional for hospitals to report this data to the hospital association.

Indiana provides the birth weight for newborn and neonates. Neonates are defined as children less than 29 days old.

Beginning in 2008, birthweight was available and used on the inpatient files.

Beginning in 2007, birthweight was 100% missing on Kentucky inpatient and outpatient files and thus was not retained on HCUP files

Kentucky hospitals provide the birth weight of the newborns in either pounds/ounces or grams. During HCUP processing birth weights coded in pounds/ounces are converted into grams.

For 2001, Maine does not collect information on birth weight directly. The information is extrapolated from the 5th digit of ICD-9-CM diagnosis codes 764-765 and provides only the midpoints of the weight ranges.

For 1990-1992, birth weight was reported by Maryland but was not processed as an HCUP variable. Beginning with 1993 discharges, birth weight is available in the HCUP Maryland data.

New Jersey documentation indicates that birth weight is reported for children under 29 days old. New Jersey restricts the values of birth weight to the range 100-9000 grams.