Skip to content
Dx

ICD-10-CM 2027 diagnosis code

O23.01Infections of kidney in pregnancy, first trimester

✓ Billable / specificCC — complication/comorbidityMaternity · age 9–64Female only

O23.01 is a valid, billable ICD-10-CM code for infections of kidney in pregnancy, first trimester. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About O23.01

O23.01 is the ICD-10-CM diagnosis code for infections of kidney in pregnancy, first trimester. It belongs to category O23 (infections of genitourinary tract in pregnancy), block O20-O29 (other maternal disorders predominantly related to pregnancy) and chapter 15 (pregnancy, childbirth and the puerperium). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within O23.0 (infections of kidney in pregnancy), O23.01 is specifically for infections of kidney in pregnancy, first trimester. Related codes cover unspecified trimester (O23.00), second trimester (O23.02) and third trimester (O23.03).

Use an additional code to identify organism (B95.-, B96.-).

As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.

In MS-DRG v44.0, it is part of the grouping logic for DRG 817 (Other Antepartum Diagnoses with O.R. Procedures with MCC, relative weight 2.0534), DRG 818 (Other Antepartum Diagnoses with O.R. Procedures with CC, relative weight 1.2942), DRG 819 (Other Antepartum Diagnoses with O.R. Procedures without CC/MCC, relative weight 0.7739), DRG 831 (Other Antepartum Diagnoses without O.R. Procedures with MCC, relative weight 1.1558), DRG 832 (Other Antepartum Diagnoses without O.R. Procedures with CC, relative weight 0.7585) and DRG 833 (Other Antepartum Diagnoses without O.R. Procedures without CC/MCC, relative weight 0.5002), in MDC 14 (Pregnancy, Childbirth and the Puerperium), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

The Medicare Code Editor treats this as a maternity diagnosis, expected only for patients age 9 through 64.

It is on the CMS list of diagnoses consistent only with female patients (the sex-conflict edit itself was retired in FY2025).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 646.61 (infections of genitourinary tract in pregnancy, delivered, with or without mention of antepartum condition) and 646.63 (infections of genitourinary tract in pregnancy, antepartum condition or complication).

Notes that apply from higher levels

Instructions written at a parent level also apply to O23.01.

› From O23 Infections of genitourinary tract in pregnancy
Excludes2
  • gonococcal infections complicating pregnancy, childbirth and the puerperium (O98.2)
  • infections with a predominantly sexual mode of transmission NOS complicating pregnancy, childbirth and the puerperium (O98.3)
  • syphilis complicating pregnancy, childbirth and the puerperium (O98.1)
  • tuberculosis of genitourinary system complicating pregnancy, childbirth and the puerperium (O98.0)
  • venereal disease NOS complicating pregnancy, childbirth and the puerperium (O98.3)
Use additional code
  • code to identify organism (B95.-, B96.-)

Broader instructions also apply from O20-O29 Other maternal disorders predominantly related to pregnancy and Chapter 15: Pregnancy, childbirth and the puerperium.

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

ICD-9-CM equivalent

Converter →
  • 646.61Infections of genitourinary tract in pregnancy, delivered, with or without mention of antepartum conditionapproximate
  • 646.63Infections of genitourinary tract in pregnancy, antepartum condition or complicationapproximate

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about O23.01

Is O23.01 billable?

Yes. O23.01 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can O23.01 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict O23.01 as a principal diagnosis.

Is O23.01 a CC or MCC?

O23.01 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.

What DRG does O23.01 group to?

O23.01 is used in the MS-DRG v44.0 logic for MS-DRG 817 (Other Antepartum Diagnoses with O.R. Procedures with MCC), MS-DRG 818 (Other Antepartum Diagnoses with O.R. Procedures with CC), MS-DRG 819 (Other Antepartum Diagnoses with O.R. Procedures without CC/MCC), MS-DRG 831 (Other Antepartum Diagnoses without O.R. Procedures with MCC), MS-DRG 832 (Other Antepartum Diagnoses without O.R. Procedures with CC) and MS-DRG 833 (Other Antepartum Diagnoses without O.R. Procedures without CC/MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for O23.01?

The CMS General Equivalence Mappings map O23.01 to ICD-9-CM 646.61 and 646.63.