2026 ICD-10-CM Diagnosis Code O12.00Gestational edema, unspecified trimester

ICD-10-CM Codes›O00-O9A›O10-O16›O12

ICD-10-CM O12.00
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

O12.00 is a billable ICD-10-CM diagnosis code for gestational edema, unspecified trimester. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 817 through 819, 831 through 833. The code is restricted by the Medicare Code Editor to maternity cases (age 9 through 64). Coders also document this condition as gestational edema. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified complications in pregnancy.

Code Identity

ICD-10-CM Code
O12.00
Billable Status
Yes — Valid for Submission
Code Describes
Gestational edema, unspecified trimester
Short Description
Gestational edema, unspecified trimester
Same as the full description in the CMS dataset.
Parent Code
O12.0
Gestational edema

Code Classification

ChapterO00-O9APregnancy, childbirth and the puerperium
SectionO10-O16Edema, proteinuria and hypertensive disorders in pregnancy, childbirth and the puerperium
CategoryO12Gestational [pregnancy-induced] edema and proteinuria without hypertension
This CodeO12.00Gestational edema, unspecified trimester

Code EditsBilling

Medicare Code Editor checks that affect claim validity for O12.00.

Maternity diagnoses
The Medicare Code Editor detects inconsistencies in maternity cases by checking a patient's age and any diagnosis on the patient's record. The maternity code edits apply to patients age ange is 9–64 years inclusive (e.g., diabetes in pregnancy, antepartum pulmonary complication).

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Gestational edema
  • Gestational edema without hypertension

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR PRG028
Other specified complications in pregnancy
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Edema

Edema means swelling caused by fluid in your body's tissues. It usually occurs in the feet, ankles and legs, but it can involve your entire body.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert O12.00 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
646.10 Edema in preg-unspec
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About O12.00Overview

Is O12.00 (Gestational edema) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report gestational edema, unspecified trimester on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does O12.00 group to?

When gestational edema, unspecified trimester is the principal diagnosis on an inpatient stay, it groups to MS-DRG 817, 818, 819, 831, 832, 833, with relative weights from 0.5229 to 1.6880 depending on complications. Higher weights mean higher Medicare reimbursement.

Who can O12.00 be reported for?

The Medicare Code Editor checks gestational edema, unspecified trimester against patient demographics: this code is intended for maternity cases (age 9 through 64). Claims outside these limits are flagged as inconsistent.

What is the ICD-9 equivalent of O12.00?

Under the General Equivalence Mappings, gestational edema, unspecified trimester converts to ICD-9-CM 646.10 (edema in preg-unspec). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.