2026 ICD-10-CM Diagnosis Code O36.1920Maternal care for other isoimmunization, second trimester, not applicable or unspecified

ICD-10-CM Codes›O00-O9A›O30-O48›O36

ICD-10-CM O36.1920
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

O36.1920 is a billable ICD-10-CM diagnosis code for maternal care for other isoimmunization, second trimester, not applicable or unspecified. The 7th character 0 shows this applies to a single gestation, or that the affected fetus is not identified. 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 Maternal care related to fetal conditions.

Code Identity

ICD-10-CM Code
O36.1920
Billable Status
Yes — Valid for Submission
Code Describes
Maternal care for other isoimmunization, second trimester, not applicable or unspecified
Short Description
Maternal care for oth isoimmun, second trimester, unsp
Parent Code
O36.192
Maternal care for other isoimmunization, second trimester

Code Classification

ChapterO00-O9APregnancy, childbirth and the puerperium
SectionO30-O48Maternal care related to the fetus and amniotic cavity and possible delivery problems
CategoryO36Maternal care for other fetal problems
This CodeO36.1920Maternal care for other isoimmunization, second trimester, not applicable or unspecified

Code EditsBilling

Medicare Code Editor checks that affect claim validity for O36.1920.

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 PRG013
Maternal care related to fetal conditions
Default principal diagnosis: inpatient Yes · outpatient Yes

Convert O36.1920 to ICD-9-CMHistory

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

ICD-9-CM
656.21 Abo isoimmunizat-deliver
Approximate The match is approximate rather than exact.
ICD-9-CM
656.23 Abo isoimmunizat-antepar
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 O36.1920Overview

Is O36.1920 (Maternal care for other isoimmunization, second trimester) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report maternal care for other isoimmunization, second trimester, not applicable or unspecified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character 0 in O36.1920 mean?

The final character 0 shows the maternal care for other isoimmunization, second trimester applies to a single gestation, or that the affected fetus cannot be identified.

What MS-DRG does O36.1920 group to?

When maternal care for other isoimmunization, second trimester, not applicable or unspecified 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 O36.1920 be reported for?

The Medicare Code Editor checks maternal care for other isoimmunization, second trimester, not applicable or unspecified 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 O36.1920?

Under the General Equivalence Mappings, maternal care for other isoimmunization, second trimester, not applicable or unspecified converts to ICD-9-CM 656.21 (abo isoimmunizat-deliver) and 656.23 (abo isoimmunizat-antepar). 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.