2026 ICD-10-CM Diagnosis Code P55.1ABO isoimmunization of newborn

ICD-10-CM Codes›P00–P96›P50-P61›P55

ICD-10-CM P55.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

P55.1 is a billable ICD-10-CM diagnosis code for ABO isoimmunization of newborn. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). Coders also document this condition as fetal anemia. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Hemolytic jaundice and perinatal jaundice.

Code Identity

ICD-10-CM Code
P55.1
Billable Status
Yes — Valid for Submission
Code Describes
ABO isoimmunization of newborn
Short Description
ABO isoimmunization of newborn
Same as the full description in the CMS dataset.
Parent Code
P55
Hemolytic disease of newborn

Code Classification

ChapterP00–P96Certain conditions originating in the perinatal period
SectionP50-P61Hemorrhagic and hematological disorders of newborn
CategoryP55Hemolytic disease of newborn
This CodeP55.1ABO isoimmunization of newborn

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Fetal anemia
  • Hemolytic disease of fetus due to ABO immunization
  • Hemolytic disease of fetus OR newborn due to ABO immunization
  • Hemolytic disease of newborn co-occurrent and due to ABO immunization
  • Neonatal anemia
  • Neonatal jaundice due to ABO incompatibility

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Abocclusion
      • hemolytic disease (newborn)
    • Anemia(essential) (general) (hemoglobin deficiency) (infantile) (primary) (profound)
      • newborn
        • due to
          • ABO (antibodies, isoimmunization, maternal/fetal incompatibility)
    • Disease, diseased
      • hemolytic (newborn)
        • due to or with
          • incompatibility
            • ABO (blood group)
    • Erythroblastosis(fetalis) (newborn)
      • due to
        • ABO (antibodies) (incompatibility) (isoimmunization)
    • Immunization
      • ABO
        • in newborn
    • Incompatibility
      • ABO
        • newborn
    • Isoimmunization NEC
      • newborn
        • ABO (blood groups)
    • Jaundice(yellow)
      • newborn
        • due to or associated with
          • ABO
            • antibodies
    • Jaundice(yellow)
      • newborn
        • due to or associated with
          • ABO
            • incompatibility, maternal/fetal
    • Jaundice(yellow)
      • newborn
        • due to or associated with
          • ABO
            • isoimmunization
    • Jaundice(yellow)
      • newborn
        • due to or associated with
          • hemolytic disease
            • ABO isoimmunization

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR PNL007
Hemolytic jaundice and perinatal jaundice
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Blood Disorders

Your blood is living tissue made up of liquid and solids. The liquid part, called plasma, is made of water, salts and protein. Over half of your blood is plasma. The solid part of your blood contains red blood cells, white blood cells and platelets.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert P55.1 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
773.1 NB hemolyt dis-abo isoim
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About P55.1Overview

Is P55.1 (Hemolytic disease of newborn) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report ABO isoimmunization of newborn on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What is the ICD-9 equivalent of P55.1?

Under the General Equivalence Mappings, ABO isoimmunization of newborn converts to ICD-9-CM 773.1 (NB hemolyt dis-abo isoim). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.