ICD-10-CM 2027 diagnosis code
P55.1ABO isoimmunization of newborn
P55.1 is a valid, billable ICD-10-CM code for abo isoimmunization of newborn. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.
Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data
About P55.1
P55.1 is the ICD-10-CM diagnosis code for ABO isoimmunization of newborn. It belongs to category P55 (hemolytic disease of newborn), block P50-P61 (hemorrhagic and hematological disorders of newborn) and chapter 16 (certain conditions originating in the perinatal period). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.
Within P55 (hemolytic disease of newborn), P55.1 is specifically for ABO isoimmunization of newborn. Related codes cover Rh isoimmunization of newborn (P55.0), other hemolytic diseases of newborn (P55.8) and unspecified (P55.9).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 794 (Neonate with Other Significant Problems, relative weight 1.4935), in MDC 15 (Newborns and Other Neonates with Conditions Originating in the Perinatal Period), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.
Before ICD-10, this condition was coded in ICD-9-CM as 773.1 (hemolytic disease of fetus or newborn due to ABO isoimmunization).
Notes that apply from higher levels
Instructions written at a parent level also apply to P55.1.
Broader instructions also apply from P50-P61 Hemorrhagic and hematological disorders of newborn and Chapter 16: Certain conditions originating in the perinatal period.
Alphabetic index entries
11 entriesTerms in the official ICD-10-CM index that lead to P55.1.
- 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
MS-DRG v44.0 grouping
All DRGs →Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.
MDC 15 · Newborns and Other Neonates with Conditions Originating in the Perinatal Period
ICD-9-CM equivalent
Converter →- 773.1Hemolytic disease of fetus or newborn due to ABO isoimmunizationapproximate
From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.
Code history
- 2016
- 2017
- 2018
- 2019
- 2020
- 2021
- 2022
- 2023
- 2024
- 2025
- 2026
- 2027
- FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
- No changes since FY2016.
Common questions about P55.1
Is P55.1 billable?
- Yes. P55.1 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can P55.1 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict P55.1 as a principal diagnosis.
Is P55.1 a CC or MCC?
- No. P55.1 is neither a CC nor an MCC under MS-DRG v44.0.
What DRG does P55.1 group to?
- P55.1 is used in the MS-DRG v44.0 logic for MS-DRG 794 (Neonate with Other Significant Problems). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.
What is the ICD-9 code for P55.1?
- The CMS General Equivalence Mappings map P55.1 to ICD-9-CM 773.1.