2026 ICD-10-CM Diagnosis Code Q89.4Conjoined twins
ICD-10-CM Codes›Q00-Q99›Q80-Q89›Q89
- Billable — Valid for Submission
- POA Exempt
- Chronic Condition
Q89.4 is a billable ICD-10-CM diagnosis code for conjoined twins. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 393 through 395. The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified congenital anomalies.
Code Identity
Code Classification
Present on Admission (POA)Billing
Q89.4 is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Anadidymus
- Anakatadidymus
- Asymmetrical conjoined twins
- Cephalothoracopagus
- Conjoined twins
- Cranial duplication
- Craniopagus
- Craniopagus frontalis
- Craniopagus occipitalis
- Craniopagus parasiticus
- Craniopagus parietalis
- Deradelphus
- Desmiognathus
- Dicephalic parapagus
- Dicephalus dipus dibrachius
- Dicephalus dipus tetrabrachius
- Dicephalus dipus tribrachius
- Dicephalus tripus tribrachius
- Dipygus
- Dithoracic parapagus
- Epignathus
- Fetal epignathus
- Fetal epignathus with conjoined twins
- Fetal neoplasm
- Fetus in fetu
- Gastrothoracopagus
- Gastrothoracopagus dipygus
- Heterodymus
- Ischiomelus
- Ischiopagus
- Janiceps
- Katadidymus
- Monocephalus
- Omphalopagus
- Opodidymus
- Parapagus
- Parasitic twin of asymmetrical conjoined twins
- Polysomia
- Pygoamorphus
- Pygodidymus
- Pygopagus
- Rachipagus
- Sternopagus
- Symmetrical conjoined twins
- Syncephalus
- Thoracodelphus
- Thoracodidymus
- Thoracomelus
- Thoracoomphalopagus
- Thoracopagus
- Thoracopagus epigastricus
- Thoracopagus parasiticus
- Thoracopagus with conjoined atria
- Thoracopagus with conjoined atria and ventricles
- Thoracopagus with separate hearts and common pericardial sac
- Thoracopagus with separate hearts and pericardial sacs
- Thoracoparacephalus
- Xiphopagus
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Inclusion Terms
- Craniopagus
- Dicephaly
- Pygopagus
- Thoracopagus
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
- Conjoined twins - Q89.4
- Craniopagus - Q89.4
- Dicephalus, dicephaly - Q89.4
- Epignathus - Q89.4
- twins - Q89.4
- Ischiopagus - Q89.4
- Janiceps - Q89.4
- Monster, monstrosity (single) - Q89.7
- twin - Q89.4
- Pygopagus - Q89.4
- Rudimentary (congenital) - See Also: Agenesis;
- respiratory organs in thoracopagus - Q89.4
- Siamese twin - Q89.4
- Sternopagus - Q89.4
- Syncephalus - Q89.4
- Thoracopagus - Q89.4
- Twin (newborn) - See Also: Newborn, twin;
- conjoined - Q89.4
- Xiphopagus - Q89.4
External Cause of Injuries IndexGuidance
References for this code in the External Cause of Injuries Index.
- Conjoined twins
- Craniopagus
- Dicephalus, dicephaly
- Double
- monster
- Epignathus
- Fusion, fused(congenital)
- twins
- Ischiopagus
- Janiceps
- Monster, monstrosity(single)
- twin
- Parasitic
- twin
- Pygopagus
- Rudimentary(congenital)
- respiratory organs in thoracopagus
- Siamese twin
- Sternopagus
- Syncephalus
- Thoracopagus
- Twin(newborn)
- conjoined
- Xiphopagus
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Thoracodidymus
conjoined twins united at the thorax.
Patient EducationClinical
Birth Defects
A birth defect is a problem that happens while a baby is developing in the mother's body. Most birth defects happen during the first 3 months of pregnancy. One out of every 33 babies in the United States is born with a birth defect.
The full article covers:
- What are birth defects?
- What causes birth defects?
- Who is at risk of having a baby with birth defects?
- How are birth defects diagnosed?
- What are the treatments for birth defects?
- Can birth defects be prevented?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert Q89.4 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About Q89.4Overview
Is Q89.4 (Other congenital malformations, not elsewhere classified) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report conjoined twins on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does Q89.4 group to?
When conjoined twins is the principal diagnosis on an inpatient stay, it groups to MS-DRG 393, 394, 395, with relative weights from 0.6490 to 1.5993 depending on complications. Higher weights mean higher Medicare reimbursement.
Is Q89.4 exempt from POA reporting?
Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for conjoined twins on inpatient claims.
What is the ICD-9 equivalent of Q89.4?
Under the General Equivalence Mappings, conjoined twins converts to ICD-9-CM 759.4 (conjoined twins). The mapping is a direct match.
Footnotes
[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:
- The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
- The condition places limitations on self-care, independent living, and social interactions.
