Q89.4 Conjoined twins

The ICD-10-CM code for Conjoined twins is Q89.4 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Chapter

17: Congenital malformations, deformations and chromosomal abnormalities (Q00-QA0)

Section

Q80-Q89: Other congenital malformations (Q80-Q89)

Category Q89

13 codes (10 billable)

FY2026 Status

Stable since FY2024

Also Known As

ICD-10-CM Alphabetic Index entries that lead to Q89.4:

• Pygopagus
• Epignathus
• Janiceps
• Siamese twin
• Dicephalus, dicephaly
• Craniopagus
• Ischiopagus
• Conjoined twins

Inclusion Terms

• Craniopagus
• Dicephaly
• Pygopagus
• Thoracopagus

U.S. Hospital Utilization

• An estimated 75 U.S. inpatient stays in 2022 included Q89.4 among the documented diagnoses.

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

POA indicator for congenital conditions/anomalies and Q00-Q99 exception

Congenital conditions and anomalies Assign “Y” for congenital conditions and anomalies except for categories Q00- Q99, Congenital anomalies, which are on the exempt list. Congenital conditions are always considered present on admission.

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)