O26.4 ICD-10-CM Code: Herpes gestationis

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for O26.4 in the official ICD-10-CM tabular list, quoted as published.

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

Notes without a marker are published on O26.4 itself; “inherited from” names the category or block whose note applies here.

Coder workflow for O26.4

MedCoder structured workflow — derived from this code’s own official record

Before you code O26.4

1. O26.4 is not reportable as written. Select the more specific code beneath it that the documentation supports. Codes are reported to the highest level of specificity the classification provides (Guidelines I.B.2).

   ReviewO26.40, O26.41, O26.42, O26.43

   See the relationships section · Guide: How to choose an ICD-10-CM code →

2. Confirm the condition is documented as complicating the pregnancy, childbirth, or the puerperium, and check the trimester where the code carries one and the fetus character where the category requires it. Chapter 15 codes belong on the maternal record only and take sequencing priority over codes from other chapters. It is the provider’s responsibility to state that a condition is not affecting the pregnancy; the trimester is assigned from the documentation (Guidelines I.C.15.a, I.C.15.a.1, I.C.15.a.3).

   Guide: How to choose an ICD-10-CM code →

Choose the right path

1. Does the documentation support one of the more specific codes beneath O26.4?
   Yes → Select that code and continue the checks below on its own page.
   No → O26.4 cannot be reported as written; query for the specificity its subcategory needs.

   ReviewO26.40, O26.41, O26.42, O26.43

Consider O26.4. Then confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement

Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).

Trimester

Assigned from the documented trimester at the encounter, or the trimester in which the condition developed for inpatient stays (Guidelines I.C.15.a.3).

Official instructions as workflow

• Excludes2 — not part of O26.4(2 notes)

  Coding workflow: The conditions named in this note are not included in O26.4. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

  See the official tabular notes · Guidelines I.A.12.b

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Don’t confuse O26.4 with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of O26.4 — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

• O30— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of maternal care related to the fetus and amniotic cavity and possible delivery problems adds O30; it is not part of this code and both may be reported when both are documented.

  Full comparison: O26.4 vs O30 →

• O48— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of maternal care related to the fetus and amniotic cavity and possible delivery problems adds O48; it is not part of this code and both may be reported when both are documented.

  Full comparison: O26.4 vs O48 →

• O98— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of maternal diseases classifiable elsewhere but complicating pregnancy, labor and delivery, and the puerperium adds O98; it is not part of this code and both may be reported when both are documented.

  Full comparison: O26.4 vs O98 →

• O99— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of maternal diseases classifiable elsewhere but complicating pregnancy, labor and delivery, and the puerperium adds O99; it is not part of this code and both may be reported when both are documented.

  Full comparison: O26.4 vs O99 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Verify Before Coding

• Not billable as written — a more specific code is required: O26.40, O26.41, O26.42, O26.43.

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 O26.4 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 2 Excludes1 notes across 2 chapters: L12 — Pemphigoid, Z03.7 — Encounter for suspected maternal and fetal conditions ruled out (via O26.-).

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

Referenced by 2 Excludes2 notes: O98 — Maternal infectious and parasitic diseases classifiable elsewhere but complicating pregnancy, childbirth and the puerperium, O99.7 — Diseases of the skin and subcutaneous tissue complicating pregnancy, childbirth and the puerperium.

These codes’ tabular lists name this diagnosis as distinct — both may be reported when both are documented.

Related Codes

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main term “Herpes, herpesvirus, herpetic”; these codes share that main term but sit in a different category of the Tabular List.

B02.24 — Postherpetic myelitis (zoster, myelitis), B02.29 — Other postherpetic nervous system involvement (zoster, neuritis, neuralgia), B02.30 — Zoster ocular disease, unspecified (eye), B02.31 — Zoster conjunctivitis (zoster, conjunctivitis), B02.32 — Zoster iridocyclitis (iridocyclitis, zoster), B02.33 — Zoster keratitis (cornea), B02.39 — Other herpes zoster eye disease (eyelid), B02.7 — Disseminated zoster (zoster, disseminated), B02.8 — Zoster with other complications (zoster, complicated NEC), B02.9 — Zoster without complications (zoster), B10.01 — Human herpesvirus 6 encephalitis (human, 6, encephalitis), B10.09 — Other human herpesvirus encephalitis (human, 7, encephalitis), B10.81 — Human herpesvirus 6 infection (human, 6, specified NEC), B10.82 — Human herpesvirus 7 infection (human, 7, specified NEC), B10.89 — Other human herpesvirus infection (human, 8), B35.0 — Tinea barbae and tinea capitis (tonsurans), B35.4 — Tinea corporis (circinatus), L12.0 — Bullous pemphigoid (circinatus, bullosus), L51.9 — Erythema multiforme, unspecified (iris), P35.2 — Congenital herpesviral [herpes simplex] infection (simplex, congenital), +27 more

Contextual Map

Every relationship of O26.4 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 O26.4 with these 4 related codes in Claim Check

Hierarchy

• O00-O9A — Chapter 15: Pregnancy, Childbirth and the Puerperium (O00-O9A) (O00-O9A)[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• O20-O29 — Other maternal disorders predominantly related to pregnancy[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Referenced by Excludes1 notes

• L12 — Pemphigoid[Excludes1]: “herpes gestationis (O26.4-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• Z03.7 — Encounter for suspected maternal and fetal conditions ruled out[Excludes1](via O26.-): “known or suspected fetal anomalies affecting management of mother, not ruled out (O26.-, O35.-, O36.-, O40.-, O41.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Referenced by Excludes2 notes

• O98 — Maternal infectious and parasitic diseases classifiable elsewhere but complicating pregnancy, childbirth and the puerperium[Excludes2]: “herpes gestationis (O26.4-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• O99.7 — Diseases of the skin and subcutaneous tissue complicating pregnancy, childbirth and the puerperium[Excludes2]: “herpes gestationis (O26.4)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Nearest codes (40)

• O26 — Maternal care for other conditions predominantly related to pregnancy[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• O26.0 — Excessive weight gain in pregnancy[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• O26.00 — Excessive weight gain in pregnancy, unspecified trimester[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• O26.01 — Excessive weight gain in pregnancy, first trimester[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• O26.02 — Excessive weight gain in pregnancy, second trimester[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• O26.03 — Excessive weight gain in pregnancy, third trimester[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• O26.1 — Low weight gain in pregnancy[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• O26.10 — Low weight gain in pregnancy, unspecified trimester[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• and 32 more

Change history

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

Common coding questions

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

Claim edits Official source data

CMS Definitions of Medicare Code Edits — v43.1 (April 2026) 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

Nearest Codes in This Family

Official ICD-10-CM classifications closest to O26.4 in its code family, with their registry titles.

• O26.3 — Retained intrauterine contraceptive device in pregnancy
• O26.30 — Retained intrauterine contraceptive device in pregnancy, unspecified trimester
• O26.31 — Retained intrauterine contraceptive device in pregnancy, first trimester
• O26.32 — Retained intrauterine contraceptive device in pregnancy, second trimester
• O26.33 — Retained intrauterine contraceptive device in pregnancy, third trimester
• O26.40 — Herpes gestationis, unspecified trimester
• O26.41 — Herpes gestationis, first trimester
• O26.42 — Herpes gestationis, second trimester
• O26.43 — Herpes gestationis, third trimester
• O26.5 — Maternal hypotension syndrome

View all codes in the O26 family