P55.1 ABO isoimmunization of newborn

The ICD-10-CM code for ABO isoimmunization of newborn is P55.1 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Chapter

16: Certain conditions originating in the perinatal period (P00-P96)

Section

P50-P61: Hemorrhagic and hematological disorders of newborn (P50-P61)

Category P55

5 codes (4 billable)

FY2026 Status

Stable since FY2024

Also Known As

ICD-10-CM Alphabetic Index entries that lead to P55.1:

• Abocclusion › hemolytic disease (newborn)
• Incompatibility › ABO › newborn
• Erythroblastosis (fetalis) (newborn) › due to › ABO (antibodies) (incompatibility) (isoimmunization)
• Immunization › ABO › in newborn
• Isoimmunization NEC › newborn › ABO (blood groups)
• 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)
• Jaundice (yellow) › newborn › due to or associated with › ABO › antibodies

U.S. Hospital Utilization

• An estimated 101,705 U.S. inpatient stays in 2023 included P55.1 among the documented diagnoses.
• 2,515 stays listed it as the principal diagnosis.

Source: National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality, 2016–2023. National survey-weighted estimates.

Official Coding Guidelines

Use of Z05 codes (newborn suspected condition ruled out)

1) Use of Z05 codes Assign a code from category Z05, Observation and evaluation of newborn for suspected diseases and conditions ruled out, to identify those instances when a healthy newborn is evaluated for a suspected condition/disease that is determined after study not to be present. Do not use a code from category Z05 when the patient is documented to have signs or symptoms of a suspected problem; in such cases code the sign or symptom.

Z05 on other than the birth record

2) Z05 on other than the birth record A code from category Z05 may also be assigned as a principal or first- listed code for readmissions or encounters when the code from category Z38 code no longer applies. Codes from category Z05 are for use only for healthy newborns and infants for which no condition after study is found to be present.

Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026

References

• CMS — ICD-10-CM Official Code Set and Guidelines, FY2026
• CDC/NCHS — ICD-10-CM Files and Browser Tool
• AHRQ — HCUP National Inpatient Sample, Frequencies by Diagnosis Code (2016–2023)