2026 ICD-10-CM Diagnosis Code O23.21Infections of urethra in pregnancy, first trimester

ICD-10-CM Codes›O00-O9A›O20-O29›O23

ICD-10-CM O23.21
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

O23.21 is a billable ICD-10-CM diagnosis code for infections of urethra in pregnancy, first trimester. 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 Other specified complications in pregnancy and Urinary tract infections.

This medical diagnosis code is frequently used in OB/GYN medical specialties to designate conditions such maternal disorders related to pregnancy.

Code Identity

ICD-10-CM Code
O23.21
Billable Status
Yes — Valid for Submission
Code Describes
Infections of urethra in pregnancy, first trimester
Short Description
Infections of urethra in pregnancy, first trimester
Same as the full description in the CMS dataset.
Parent Code
O23.2
Infections of urethra in pregnancy

Code Classification

ChapterO00-O9APregnancy, childbirth and the puerperium
SectionO20-O29Other maternal disorders predominantly related to pregnancy
CategoryO23Infections of genitourinary tract in pregnancy
This CodeO23.21Infections of urethra in pregnancy, first trimester

Code EditsBilling

Medicare Code Editor checks that affect claim validity for O23.21.

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 PRG028
Other specified complications in pregnancy
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR GEN004
Urinary tract infections
Default principal diagnosis: inpatient No · outpatient No

Patient EducationClinical

Infections and Pregnancy

During pregnancy, some common infections such as the common cold or a skin infection do not usually cause serious problems. Some infections, such as the flu, can be more severe when you're pregnant. But other infections can be harmful to you, your fetus, or both.

The full article covers:

  • How can infections affect your pregnancy?
  • What infections can be harmful during pregnancy?
  • What are the symptoms of an infection during pregnancy?
  • What are the treatments for infections during pregnancy?
  • Can infections during pregnancy be prevented?

Read the full article at MedlinePlus

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

Convert O23.21 to ICD-9-CMHistory

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

ICD-9-CM
646.61 Gu infection-delivered
Approximate The match is approximate rather than exact.
ICD-9-CM
646.63 Gu infection-antepartum
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 O23.21Overview

Is O23.21 (Infections of urethra in pregnancy) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report infections of urethra in pregnancy, first trimester on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does O23.21 group to?

When infections of urethra in pregnancy, first trimester 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 O23.21 be reported for?

The Medicare Code Editor checks infections of urethra in pregnancy, first trimester 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 O23.21?

Under the General Equivalence Mappings, infections of urethra in pregnancy, first trimester converts to ICD-9-CM 646.61 (gu infection-delivered) and 646.63 (gu infection-antepartum). 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.