Alphabetic Index FY2027

P55.1

ABO isoimmunization of newborn

FY2027Chapter 16: Certain conditions originating in the perinatal period/P50–P61 Hemorrhagic and hematological disorders of newborn

BillableComplete code, valid to report
Care settingsHome Health Primary · MMTA - Other

P55.1 (also written P551) is a billable ICD-10-CM diagnosis code for ABO isoimmunization of newborn. It is part of the FY2027 code set, effective October 1, 2026. It is one of the 4 codes in category P55 (Hemolytic disease of newborn). The Alphabetic Index lists it under 11 entries. Its coding notes include 5 Excludes1 entries and 5 Excludes2 entries.

Guidelines tip

From the FY2027 Official Guidelines. ICD10Ref adds no rules of its own.

Chapter 16 codes are never used on the maternal record, and chapter 15 codes are never used on the newborn record. Chapter 16 codes can be used for life if the condition persists.

Guidelines I.C.16.a.1Perinatal codes and the maternal recordRead the official text

Excludes1

Not coded here. The listed conditions generally should not be reported together.

Also from chapter/block level (5 notes)
Inherited from P50–P61 Hemorrhagic and hematological disorders of newborn
  • congenital stenosis and stricture of bile ducts (Q44.3)
  • Crigler-Najjar syndrome (E80.5)
  • Dubin-Johnson syndrome (E80.6)
  • Gilbert syndrome (E80.4)
  • hereditary hemolytic anemias (D55-D58)

Excludes2

Not included here. Both codes may be reported if the patient has both conditions.

Also from chapter/block level (5 notes)
Inherited from Chapter 16 Certain conditions originating in the perinatal period
  • congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • tetanus neonatorum (A33)

Care settings

How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.

Home Health Primary

Accepted as the primary (principal) diagnosis on a home health claim. The Home Health Grouper assigns it to the MMTA - Other clinical group.

Source: CMS Home Health Grouper Software v07.2.26, effective October 1, 2026

Includes

Further defines or gives examples of the content of the category.

Also from chapter/block level (1 note)
Inherited from Chapter 16 Certain conditions originating in the perinatal period
  • conditions that have their origin in the fetal or perinatal period (before birth through the first 28 days after birth) even if morbidity occurs later

Notes

Also from chapter/block level (1 note)
Inherited from Chapter 16 Certain conditions originating in the perinatal period
  • Codes from this chapter are for use on newborn records only, never on maternal records

Alphabetic Index terms

Terms the official Alphabetic Index lists for this code. 11 entries