2027 ICD-10-CM Diagnosis Code O41.1230Chorioamnionitis, third trimester, not applicable or unspecified

ICD-10-CM Codes›O00-O9A›O30-O48›O41

ICD-10-CM O41.1230
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

O41.1230 is a billable ICD-10-CM diagnosis code for chorioamnionitis, third 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 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 817 through 819, 831 through 833. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 63 closely related codes. 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 intrauterine infection.

Code Identity

ICD-10-CM Code
O41.1230
Billable Status
Yes — Valid for Submission
Code Describes
Chorioamnionitis, third trimester, not applicable or unspecified
Short Description
Chorioamnionitis, third trimester, not applicable or unsp
Parent Code
O41.123
Chorioamnionitis, third trimester

Code Classification

ChapterO00-O9APregnancy, childbirth and the puerperium
SectionO30-O48Maternal care related to the fetus and amniotic cavity and possible delivery problems
CategoryO41Other disorders of amniotic fluid and membranes
This CodeO41.1230Chorioamnionitis, third trimester, not applicable or unspecified

Code EditsBilling

Medicare Code Editor checks that affect claim validity for O41.1230.

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).

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to O41.1230: its own notes plus those printed at O41 and Chapter 15. A note printed at a category, block or chapter applies to every code under it.

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From O41 Other disorders of amniotic fluid and membranes applies to 168 codes
  • encounter for suspected maternal and fetal conditions ruled out (Z03.7-)
From Chapter 15 (O00-O9A) Pregnancy, childbirth and the puerperium applies to 2,481 codes
  • supervision of normal pregnancy (Z34.-)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 15 (O00-O9A) Pregnancy, childbirth and the puerperium applies to 2,481 codes
  • mental and behavioral disorders associated with the puerperium (F53.-)
  • obstetrical tetanus (A34)
  • postpartum necrosis of pituitary gland (E23.0)
  • puerperal osteomalacia (M83.0)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Chapter 15 (O00-O9A) Pregnancy, childbirth and the puerperium applies to 2,481 codes
  • code, if applicable, from category Z3A, Weeks of gestation, to identify the specific week of the pregnancy, if known.

Notes

General instructions on how these codes are used.

From Chapter 15 (O00-O9A) Pregnancy, childbirth and the puerperium applies to 2,481 codes
  • CODES FROM THIS CHAPTER ARE FOR USE ONLY ON MATERNAL RECORDS, NEVER ON NEWBORN RECORDS
  • Codes from this chapter are for use for conditions related to or aggravated by the pregnancy, childbirth, or by the puerperium (maternal causes or obstetric causes)
  • Trimesters are counted from the first day of the last menstrual period. They are defined as follows:
  • 1st trimester- less than 14 weeks 0 days
  • 2nd trimester- 14 weeks 0 days to less than 28 weeks 0 days
  • 3rd trimester- 28 weeks 0 days until delivery

7th Character

Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.

From O41 Other disorders of amniotic fluid and membranes applies to 168 codes
  • One of the following 7th characters is to be assigned to each code under category O41. 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 O41 that has a 7th character of 1 through 9.
Values for category O41 Fetus Identification
  • 0not applicable or unspecified this code
  • 1fetus 1
  • 2fetus 2
  • 3fetus 3
  • 4fetus 4
  • 5fetus 5
  • 9other fetus

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name O41.1230, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming O41.1230: they are not reported together with it, unless the two conditions are unrelated.

  • Z03.7 Encounter for suspected maternal and fetal conditions ruled out
    known or suspected fetal anomalies affecting management of mother, not ruled out (O26.-, O35.-, O36.-, O40.-, O41.-) names O41.-, which includes this code

Clinical ClassificationClinical

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

CCSR PRG021
Maternal intrauterine infection
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Chorioamnionitis

    inflammation of the placental membranes (chorion; amnion) and connected tissues such as fetal blood vessels and umbilical cord. it is often associated with intrauterine ascending infections during pregnancy.

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 O41.1230 to ICD-9-CMHistory

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

ICD-9-CM
658.41 Amniotic infection-deliv
Approximate The match is approximate rather than exact.
ICD-9-CM
658.43 Amniotic infect-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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About O41.1230Overview

What is the ICD-10 code for chorioamnionitis, third trimester, not applicable or unspecified?

The ICD-10-CM code for chorioamnionitis, third trimester, not applicable or unspecified is O41.1230 (sometimes written as O411230). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is O41.1230 (Chorioamnionitis, third trimester) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report chorioamnionitis, third trimester, not applicable or unspecified on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What does the 7th character 0 in O41.1230 mean?

The final character 0 shows the chorioamnionitis, third trimester applies to a single gestation, or that the affected fetus cannot be identified.

What MS-DRG does O41.1230 group to?

When chorioamnionitis, third trimester, not applicable or unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 833, 832, 831, 819, 818, 817, with relative weights from 0.5000 to 1.7586 depending on complications. Higher weights mean higher Medicare reimbursement.

Is O41.1230 a CC or MCC?

CMS lists O41.1230 as an MCC (major complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 63 closely related codes in its exclusion list.