2026 ICD-10-CM Diagnosis Code O31.33X4Continuing pregnancy after elective fetal reduction of one fetus or more, third trimester, fetus 4

ICD-10-CM Codes›O00-O9A›O30-O48›O31

ICD-10-CM O31.33X4
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

O31.33X4 is a billable ICD-10-CM diagnosis code for continuing pregnancy after elective fetal reduction of one fetus or more, third trimester, fetus 4. The 7th character 4 identifies fetus 4 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 Multiple gestation.

Code Identity

ICD-10-CM Code
O31.33X4
Billable Status
Yes — Valid for Submission
Code Describes
Continuing pregnancy after elective fetal reduction of one fetus or more, third trimester, fetus 4
Short Description
Cont preg aft elctv fetl rdct of 1 fts or more,3rd tri, fts4
Parent Code
O31.33
Continuing pregnancy after elective fetal reduction of one fetus or more, third trimester

Code Classification

ChapterO00-O9APregnancy, childbirth and the puerperium
SectionO30-O48Maternal care related to the fetus and amniotic cavity and possible delivery problems
CategoryO31Complications specific to multiple gestation
This CodeO31.33X4Continuing pregnancy after elective fetal reduction of one fetus or more, third trimester, fetus 4

Code EditsBilling

Medicare Code Editor checks that affect claim validity for O31.33X4.

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 PRG012
Multiple gestation
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Abortion

An induced abortion is a procedure to end a pregnancy. It can be done two different ways:

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Convert O31.33X4 to ICD-9-CMHistory

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

ICD-9-CM
651.71 Mult gest-fet reduct del
Approximate The match is approximate rather than exact.
ICD-9-CM
651.73 Mul gest-fet reduct ante
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 O31.33X4Overview

Is O31.33X4 a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report continuing pregnancy after elective fetal reduction of one fetus or more, third trimester, fetus 4 on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character 4 in O31.33X4 mean?

The final character 4 identifies the fetus in a multiple gestation pregnancy: this code reports continuing pregnancy after elective fetal reduction of one fetus or more, third trimester for fetus 4.

What MS-DRG does O31.33X4 group to?

When continuing pregnancy after elective fetal reduction of one fetus or more, third trimester, fetus 4 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 O31.33X4 be reported for?

The Medicare Code Editor checks continuing pregnancy after elective fetal reduction of one fetus or more, third trimester, fetus 4 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 O31.33X4?

Under the General Equivalence Mappings, continuing pregnancy after elective fetal reduction of one fetus or more, third trimester, fetus 4 converts to ICD-9-CM 651.71 (mult gest-fet reduct del) and 651.73 (mul gest-fet reduct ante). 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.