2026 ICD-10-CM Diagnosis Code O40.2XX1Polyhydramnios, second trimester, fetus 1

ICD-10-CM Codes›O00-O9A›O30-O48›O40

ICD-10-CM O40.2XX1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

O40.2XX1 is a billable ICD-10-CM diagnosis code for polyhydramnios, second trimester, fetus 1. The 7th character 1 identifies fetus 1 in a multiple gestation pregnancy. 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). In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Polyhydramnios and other problems of amniotic cavity.

Code Identity

ICD-10-CM Code
O40.2XX1
Billable Status
Yes — Valid for Submission
Code Describes
Polyhydramnios, second trimester, fetus 1
Short Description
Polyhydramnios, second trimester, fetus 1
Same as the full description in the CMS dataset.
Parent Code
O40.2
Polyhydramnios, second trimester

Code Classification

ChapterO00-O9APregnancy, childbirth and the puerperium
SectionO30-O48Maternal care related to the fetus and amniotic cavity and possible delivery problems
CategoryO40Polyhydramnios
This CodeO40.2XX1Polyhydramnios, second trimester, fetus 1

Code EditsBilling

Medicare Code Editor checks that affect claim validity for O40.2XX1.

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).

Clinical ClassificationClinical

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

CCSR PRG014
Polyhydramnios and other problems of amniotic cavity
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Health Problems in Pregnancy

A health problem in pregnancy is any disease or condition that could affect your health or the health of your fetus. Some health problems may make it more likely that you will have a high-risk pregnancy. A high-risk pregnancy is one in which you, your fetus, or both are at higher risk for health problems than in a typical pregnancy.

The full article covers:

  • What are health problems in pregnancy?
  • What raises my risk for health problems during pregnancy?
  • Can chronic health conditions cause problems in pregnancy?
  • Can health problems in pregnancy be prevented?

Read the full article at MedlinePlus

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

Convert O40.2XX1 to ICD-9-CMHistory

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

ICD-9-CM
657.01 Polyhydramnios-delivered
Approximate The match is approximate rather than exact.
ICD-9-CM
657.03 Polyhydramnios-antepart
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 O40.2XX1Overview

Is O40.2XX1 (Polyhydramnios, second trimester) a billable code?

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

What does the 7th character 1 in O40.2XX1 mean?

The final character 1 identifies the fetus in a multiple gestation pregnancy: this code reports polyhydramnios, second trimester for fetus 1.

What MS-DRG does O40.2XX1 group to?

When polyhydramnios, second trimester, fetus 1 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 O40.2XX1 be reported for?

The Medicare Code Editor checks polyhydramnios, second trimester, fetus 1 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 O40.2XX1?

Under the General Equivalence Mappings, polyhydramnios, second trimester, fetus 1 converts to ICD-9-CM 657.01 (polyhydramnios-delivered) and 657.03 (polyhydramnios-antepart). 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.