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Q00.0 ICD-10-CM Code: Anencephaly

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Coding at a Glance

Tabular directives
5 inclusion terms
Risk adjustment
CMS-HCC V28: 1 category · CMS-HCC V22 category 72 · RxHCC V08 category 155

Inpatient Payment Groups (MS-DRG)

Potential MS-DRG participation — not a DRG assignment.

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v43, Appendix B.

  • MS-DRG 091 — OTHER DISORDERS OF NERVOUS SYSTEM WITH MCC (MDC 01)
  • MS-DRG 092 — OTHER DISORDERS OF NERVOUS SYSTEM WITH CC (MDC 01)
  • MS-DRG 093 — OTHER DISORDERS OF NERVOUS SYSTEM WITHOUT CC/MCC (MDC 01)
  • MS-DRG 791 — PREMATURITY WITH MAJOR PROBLEMS (MDC 15)
  • MS-DRG 793 — FULL TERM NEONATE WITH MAJOR PROBLEMS (MDC 15)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Risk Adjustment (CMS-HCC)

Payment categories this diagnosis maps to under CMS-HCC V28, payment year 2026.

  • HCC 182 — Spinal Cord Disorders/Injuries

Other models: CMS-HCC V22 HCC 72 · RxHCC V08 HCC 155

Risk scores depend on the enrollee's full accepted diagnosis set and segment; a category mapping alone does not determine payment.

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for Q00.0 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Inclusion Terms

Alternative terms the tabular list files under this code.

  • Acephaly
  • Acrania
  • Amyelencephaly
  • Hemianencephaly
  • Hemicephaly

Code Overview

Anencephaly is a billable ICD-10-CM diagnosis code (Q00.0).

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Indexed Clinical Terms (22)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

Official Coding Guidelines

Official source data — quoted verbatim from the CMS/NCHS Official Guidelines

Official source data — quoted verbatim from the CMS/NCHS Official Guidelines

Verbatim excerpts from the ICD-10-CM Official Guidelines for Coding and Reporting (CMS/NCHS) that govern this code.

Chapter 17: Congenital malformations, deformations, and chromosomal abnormalities (Q00-QA1)

Assign an appropriate code(s) from categories Q00-QA1, Congenital malformations, deformations, and chromosomal abnormalities when a malformation/deformation or chromosomal abnormality is documented. A malformation/deformation/or chromosomal abnormality may be the principal/first-listed diagnosis on a record or a secondary diagnosis.

Chapter 17: Congenital malformations, deformations, and chromosomal abnormalities (Q00-QA1)

Codes from Chapter 17 may be used throughout the life of the patient. If a congenital malformation or deformity has been corrected, a personal history code should be used to identify the history of the malformation or deformity. Although present at birth, a malformation/deformation/or chromosomal abnormality may not be identified until later in life. Whenever the condition is diagnosed by the provider, it is appropriate to assign a code from codes Q00-QA1. For the birth admission, the appropriate code from category Z38, Liveborn infants, according to place of birth and type of delivery, should be sequenced as the principal diagnosis, followed by any congenital anomaly codes, Q00- QA1.

Verify Before Coding

  • MCC as a secondary diagnosis (FY2026). Can raise the stay's MS-DRG severity tier.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name Q00.0 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 1 Excludes1 note: Q75 — Other congenital malformations of skull and face bones.

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

MS-DRG Grouper Relationships (FY2026)

Potential MS-DRG participation — not a DRG assignment.

FY2026 MS-DRG: MCC — Major Complication or Comorbidity. Reported as a secondary diagnosis, this code raises the stay's MS-DRG severity tier — except when the principal diagnosis is one of 3 clinically related codes on its CMS exclusion list.

Named in the grouper logic of 5 MS-DRGs: DRG 091 (MDC 01), DRG 092 (MDC 01), DRG 093 (MDC 01), DRG 791 (MDC 15), DRG 793 (MDC 15).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):MAL004 — Nervous system congenital anomalies (default).

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same clinical process (MS-DRG)

Acts as MCC — raises the severity of other admissions. CMS groups these diagnoses into one MS-DRG principal-diagnosis exclusion process — a CC/MCC on this list never raises severity when the principal diagnosis is also on it.

Q00.1 — Craniorachischisis, Q00.2 — Iniencephaly

Same CMS-HCC risk category (V28)

CMS maps these diagnoses to the same Hierarchical Condition Category (Spinal Cord Disorders/Injuries) for risk-adjusted payment.

G95.0 — Syringomyelia and syringobulbia, G95.11 — Acute infarction of spinal cord (embolic) (nonembolic), G95.19 — Other vascular myelopathies, G95.20 — Unspecified cord compression, G95.29 — Other cord compression, G95.81 — Conus medullaris syndrome, G95.89 — Other specified diseases of spinal cord, G95.9 — Disease of spinal cord, unspecified, G99.2 — Myelopathy in diseases classified elsewhere, P11.5 — Birth injury to spine and spinal cord, Q00.1 — Craniorachischisis, Q00.2 — Iniencephaly, Q01.0 — Frontal encephalocele, Q01.1 — Nasofrontal encephalocele, Q01.2 — Occipital encephalocele, Q01.8 — Encephalocele of other sites, Q01.9 — Encephalocele, unspecified, Q02 — Microcephaly, Q03.0 — Malformations of aqueduct of Sylvius, Q03.1 — Atresia of foramina of Magendie and Luschka, +230 more

Related risk categories

These categories interact through CMS's HCC hierarchy — one can suppress the other's risk-adjustment weight when both are present on a claim.

Quadriplegia, Paraplegia

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Nervous system congenital anomalies).

Q00.1 — Craniorachischisis, Q00.2 — Iniencephaly, Q01.0 — Frontal encephalocele, Q01.1 — Nasofrontal encephalocele, Q01.2 — Occipital encephalocele, Q01.8 — Encephalocele of other sites, Q01.9 — Encephalocele, unspecified, Q02 — Microcephaly, Q03.0 — Malformations of aqueduct of Sylvius, Q03.1 — Atresia of foramina of Magendie and Luschka, Q03.8 — Other congenital hydrocephalus, Q03.9 — Congenital hydrocephalus, unspecified, Q04.0 — Congenital malformations of corpus callosum, Q04.1 — Arhinencephaly, Q04.2 — Holoprosencephaly, Q04.3 — Other reduction deformities of brain, Q04.4 — Septo-optic dysplasia of brain, Q04.5 — Megalencephaly, Q04.6 — Congenital cerebral cysts, Q04.8 — Other specified congenital malformations of brain, +29 more

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main terms “Hypoplasia, hypoplastic”, “Anomaly, anomalous”, “Deformity”, …; these codes share that main term but sit in a different category of the Tabular List.

N94.89 — Other specified conditions associated with female genital organs and menstrual cycle (genitalia, genital organor system NEC, female, acquired), O33.0 — Maternal care for disproportion due to deformity of maternal pelvic bones (pelvis, pelvic, with disproportion), O33.7 — Maternal care for disproportion due to other fetal deformities (fetal, with fetopelvic disproportion), O33.8 — Maternal care for disproportion of other origin (lumbar spine, with disproportion), O34.8 — Maternal care for other abnormalities of pelvic organs (soft parts, organs or tissues, in pregnancy or childbirth NEC), O65.0 — Obstructed labor due to deformed pelvis (lumbar spine, with disproportion, causing obstructed labor), O65.5 — Obstructed labor due to abnormality of maternal pelvic organs (soft parts, organs or tissues, in pregnancy or childbirth NEC, causing obstructed labor), O66.3 — Obstructed labor due to other abnormalities of fetus (fetal, causing obstructed labor), P28.0 — Primary atelectasis of newborn (pulmonary, associated with short gestation), P83.5 — Congenital hydrocele (genitalia, genital organor system, male, hydrocele), Q02 — Microcephaly (brain), Q03.0 — Malformations of aqueduct of Sylvius (aqueduct of Sylvius), Q03.1 — Atresia of foramina of Magendie and Luschka (Dandy-Walker), Q03.9 — Congenital hydrocephalus, unspecified (skull, with, hydrocephalus), Q04.0 — Congenital malformations of corpus callosum (corpus callosum), Q04.3 — Other reduction deformities of brain (cerebellum), Q04.8 — Other specified congenital malformations of brain (gyri), Q04.9 — Congenital malformation of brain, unspecified (brain), Q05.9 — Spina bifida, unspecified (meningocele), Q06.0 — Amyelia (spinal cord), +603 more

Contextual Map

Every relationship of Q00.0 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run Q00.0 with this related code in Claim Check

Hierarchy

Referenced by Excludes1 notes

Clinical classification (CCSR)

Risk adjustment (CMS-HCC)

  • HCC 182 — Spinal Cord Disorders/Injuries [CMS-HCC]— CMS-HCC V28 · 2026

MS-DRG Grouper

MDC crossing

  • MDC 01 — Diseases and Disorders of the Nervous System[MDC crossing]: “Diseases and Disorders of the Nervous System — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 8,892 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026
  • MDC 15 — Newborns and Other Neonates with Conditions Originating in Perinatal Period[MDC crossing]: “Newborns and Other Neonates with Conditions Originating in Perinatal Period — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs.”— CMS MS-DRG Definitions Manual · FY2026

Index entries (22)

  • Absence (of) (organ or part) (complete or partial), brain[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Absence (of) (organ or part) (complete or partial), skull bone (congenital), with, anencephaly[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Acephalia, acephalism, acephalus, acephaly[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Acrania[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Agenesis, brain[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Agenesis, skull (bone), with, anencephaly[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Amyelencephalus, amyelencephaly[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Anencephalus, anencephaly[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • and 14 more

Nearest codes

Change history

  • FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page
Coding guidelines Official source data
ICD-10-CM Official Guidelines for Coding and Reporting (FY2026), quoted by section Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page
Inpatient payment groups Official source data
CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v43 Release, file and checksum · Publisher’s page
Risk adjustment Official source data
2026 Mid-Year Final ICD-10 Mappings + Model Software (cms.gov/files/zip/2026-midyear-final-icd-10-mappings.zip, 2026-midyear-final-model-software.zip) — CMS-HCC V28, PY2026 mid-year final release Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder structured relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "Q00.0 — Anencephaly." ICD-10-CM FY2026. https://medcoder.ai/icd10/code/q00.0-anencephaly

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Anencephaly

No changes since FY2016 — additions, deletions, description changes and billable-status changes are tracked through FY2027 (effective October 1, 2026), and none are recorded for this code. Note changes are tracked from FY2027 only.

Nearest Codes in This Family

Official ICD-10-CM classifications closest to Q00.0 in its code family, with their registry titles.

View all codes in the Q00 family