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

District of Columbia supplied birth weight for all patients. HCUP only retained the birth weight for patients with an age in years of 0.

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 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.

Because of the timing of HCUP data processing for the 1999 NIS, the Massachusetts source file provided to HCUP was an interim file for the construction of the 1999 SID and NIS that included records that had failed edit checks. The percent of failed records is very small, ranging from 0.0% to 1.5% (with a mean of 0.4%) for most hospitals. A handful of hospitals had a large percent of failed records. Failed records have one or more of the following errors:

• Invalid diagnosis code *
• Invalid procedure code *
• Invalid or missing birth weight
• Invalid claim certificate number **
• Invalid or inconsistent UB-92 revenue code
• Invalid medical record or person number
• Invalid type of payer *
• Inconsistent primary and secondary payer
• Invalid physician identifier
• Invalid patient or employer ZIP Code. **

* These errors would have been handled during HCUP data processing.

** These data elements are not included in the HCUP data files.

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.

New York restricts the values of birth weight. Values less than 100 grams are set to 100; values greater than 9000 grams are set to 9000 grams.

Beginning with the 2008 data, the HCUP data element BWT is missing (.) for AIDS/HIV patients. New York identifies AIDS/HIV records by ICD-9-CM diagnosis code, DRG, or MS-DRG:

• An admitting, principal or any secondary diagnosis of "042", "043", "044", "7958", "27910", "27919", "2793", "1363", "79571", "07951", "07952", "07953", "V017" or "V08".
• A DRG of 488 through 490 (prior to October 2007) or MS-DRG of 700 through 716 (beginning in October 2007).

Please note that the admitting diagnosis is not retained in the HCUP databases prior to 2012.