ICD-9-CM Diagnosis Code 656.21
Diagnosis Code: 656.21 (Raw: 65621)
Description: Isoimmunization from other and unspecified blood-group incompatibility, delivered, with or without mention of antepartum condition
Classification: International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM)
Fiscal Year: 2026 Reference
CMS Section 111 Status: Valid for reporting.
Overview & Historical Usage
ICD-9-CM code 656.21 is designated for Isoimmunization from other and unspecified blood-group incompatibility, delivered, with or without mention of antepartum condition. While superseded by ICD-10 for current healthcare encounters, it remains a recognized reference code for CMS Section 111 reporting, legacy claims adjudication, and historical clinical data analysis.