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O40.1 ICD-10-CM Code: Polyhydramnios, first trimester

Billing Status: NO. This is a clinician non-billable / parent hierarchy grouping in the ICD-10-CM system.

Coding at a Glance

7th character
Required — see the character table on this page
Tabular directives
1 inclusion term · 1 Excludes1

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for O40.1 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 O40.1 itself; “inherited from” names the category or block whose note applies here.

Includes

Conditions the official ICD-10-CM tabular list includes under this code.

  • hydramnios

Source: inherited from O40

Excludes1 — Not Coded Here

Conditions generally not reported together with this code (Excludes1) -- an error unless the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Source: inherited from O40

7th Character Guide

"One of the following 7th characters is to be assigned to each code under category O40. 7th character 0 is for single gestations and multiple gestations where the fetus is unspecified. 7th characters 1 through 9 are for cases of multiple gestations to identify the fetus for which the code applies. The appropriate code from category O30, Multiple gestation, must also be assigned when assigning a code from category O40 that has a 7th character of 1 through 9."

  • 0 — not applicable or unspecified
  • 1 — fetus 1
  • 2 — fetus 2
  • 3 — fetus 3
  • 4 — fetus 4
  • 5 — fetus 5
  • 9 — other fetus

Variant codes in this family

O40.1XX0, O40.1XX1, O40.1XX2, O40.1XX3, O40.1XX4, O40.1XX5, O40.1XX9

Character meanings are CMS's official 7th-character extensions for this family, as carried in each variant code's official description; variant codes are registry rows. The explanation of how the encounter character is assigned is MedCoder editorial, distinct from the official content above it.

Coder workflow for O40.1

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

Before you code O40.1

  1. O40.1 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).

    ReviewO40.1XX0, O40.1XX1, O40.1XX2, O40.1XX3, O40.1XX4, O40.1XX5, O40.1XX9

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

  2. A 7th character is required in this family. Confirm the documentation supports the character assigned — its meaning in this family is defined in the official instruction. O40.1 is not valid without one. The official 7th-character definitions for this family are quoted in the guide.

    See the 7th Character Guide

  3. 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 →

  4. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with O40.1. Excludes1 conditions are not reported together with this code unless the record shows they are unrelated (Guidelines I.A.12.a).

    See the official tabular notes

Choose the right path

  1. Does the documentation support one of the more specific codes beneath O40.1?
    Yes → Select that code and continue the checks below on its own page.
    No → O40.1 cannot be reported as written; query for the specificity its subcategory needs.

    ReviewO40.1XX0, O40.1XX1, O40.1XX2, O40.1XX3, O40.1XX4, O40.1XX5, O40.1XX9

  2. Does the documentation support a condition named in O40.1’s Excludes1 note?
    Yes → Do not simply proceed: review the excluded code. Both are reported only when the record shows the two conditions are unrelated.
    No → Continue.

    ReviewZ03.7

  3. Does the documentation support one of this family’s 7th-character values?
    Yes → Assign the matching 7th character; the variant codes are in the 7th Character Guide.
    No → The code is invalid without its 7th character — query for the missing element.

Consider O40.1. 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).
7th-character basis
The documented element this family’s 7th character records (see the official definitions in the 7th Character Guide).
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

  • Excludes1 — check before selecting O40.1(1 note)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with O40.1: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareZ03.7

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

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Documentation: Both the condition O40.1 describes and a condition named in its Excludes1 note are documented for the same encounter.

Coding question: Can both codes be reported?

Path: Review the Excludes1 note and the excluded code, and look for a provider statement on whether the two conditions are related.

Reason: Excludes1 means the two are not coded together; the exception is when the record shows the conditions are unrelated to each other (Guidelines I.A.12.a).

ReviewZ03.7

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.

Code Overview

Polyhydramnios, first trimester is a non-billable ICD-10-CM category code (O40.1). A more specific billable subcode must be selected for claims submission.

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

Verify Before Coding

  • Not billable as written — a more specific code is required: O40.1XX0, O40.1XX1, O40.1XX2, O40.1XX3, O40.1XX4.
  • Requires a 7th character. "One of the following 7th characters is to be assigned to each code under category O40. 7th character 0 is for single gestations and multiple gestations where the fetus is unspecified. 7th characters 1 through 9 are for cases of multiple gestations to identify the fetus for which the code applies. The appropriate code from category O30, Multiple gestation, must also be assigned when assigning a code from category O40 that has a 7th character of 1 through 9." Options: O40.1XX0, O40.1XX1, O40.1XX2, O40.1XX3, O40.1XX4, O40.1XX5

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 O40.1 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: Z03.7 — Encounter for suspected maternal and fetal conditions ruled out (via O40.-).

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

Referenced by 10 Excludes2 notes: O20 — Hemorrhage in early pregnancy (via O40.-), O20-O29 — Other maternal disorders predominantly related to pregnancy (O20-O29) (via O40.-), O21 — Excessive vomiting in pregnancy (via O40.-), O22 — Venous complications and hemorrhoids in pregnancy (via O40.-), O23 — Infections of genitourinary tract in pregnancy (via O40.-), O24 — Diabetes mellitus in pregnancy, childbirth, and the puerperium (via O40.-), O25 — Malnutrition in pregnancy, childbirth and the puerperium (via O40.-), O26 — Maternal care for other conditions predominantly related to pregnancy (via O40.-), O28 — Abnormal findings on antenatal screening of mother (via O40.-), O29 — Complications of anesthesia during pregnancy (via O40.-).

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

Contextual Map

Every relationship of O40.1 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 O40.1 with these 9 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes

Referenced by Excludes2 notes (10)

Nearest codes (32)

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

Can O40.1 be billed directly?

No. O40.1 (Polyhydramnios, first trimester) is a non-billable ICD-10-CM category code. A more specific billable subcode must be selected based on clinical documentation.

Does O40.1 require a 7th character?

Yes. One of the following 7th characters is to be assigned to each code under category O40. 7th character 0 is for single gestations and multiple gestations where the fetus is unspecified. 7th characters 1 through 9 are for cases of multiple gestations to identify the fetus for which the code applies. The appropriate code from category O30, Multiple gestation, must also be assigned when assigning a code from category O40 that has a 7th character of 1 through 9..

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

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. "O40.1 — Polyhydramnios, first trimester." ICD-10-CM FY2026. https://medcoder.ai/icd10/code/o40.1-polyhydramnios-first-trimester

Change history

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

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 O40.1 in its code family, with their registry titles.

View all codes in the O40 family