2026 ICD-10-CM Diagnosis Code O41.1290Chorioamnionitis, unspecified trimester, not applicable or unspecified
O41.1290 is a billable ICD-10-CM diagnosis code for chorioamnionitis, unspecified 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 intrauterine infection.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for O41.1290.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Acute chorioamnionitis
- Chorioamnionitis
- Chorioamnionitis caused by Bacteria
- Chorioamnionitis caused by fungus
- Chorioamnionitis caused by virus
- Fetal disorder due to amnionitis
- Fetal disorder due to chorioamnionitis
- Fetal disorder due to disorder of amniotic cavity and/or membrane
- Placentitis
- Subchorionic intervillositis
- Villitis
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
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.Chorioamnionitis
a morphologic finding indicating inflammation of the fetal sac membranes. it is characterized by neutrophilic infiltration of the amnion and chorion.Clinical Chorioamnionitis
inflammation of the fetal sac membranes, characterized by otherwise unexplained fever (at or above 38 degree c (100.4f)) with one or more of the following: uterine tenderness and/or irritability, leukocytosis, fetal tachycardia, maternal tachycardia, or malodorous vaginal discharge.Histologic Chorioamnionitis|Acute Amnionitis|Acute Chorioamnionitis|Acute Choriodeciduitis|Acute Chorionitis|Microscopic Chorioamnionitis
inflammation of the fetal sac membranes that is characterized by neutrophilic infiltration of the amnion and chorion.
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 O41.1290 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About O41.1290Overview
Is O41.1290 (Chorioamnionitis, unspecified trimester) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report chorioamnionitis, unspecified trimester, not applicable or unspecified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character 0 in O41.1290 mean?
The final character 0 shows the chorioamnionitis, unspecified trimester applies to a single gestation, or that the affected fetus cannot be identified.
What MS-DRG does O41.1290 group to?
When chorioamnionitis, unspecified 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 O41.1290 be reported for?
The Medicare Code Editor checks chorioamnionitis, unspecified 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 O41.1290?
Under the General Equivalence Mappings, chorioamnionitis, unspecified trimester, not applicable or unspecified converts to ICD-9-CM 658.40 (amniotic infection-unsp). 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.
