2027 ICD-10-CM Diagnosis Code O99.323Drug use complicating pregnancy, third trimester

ICD-10-CM Codes›O00-O9A›O94-O9A›O99

ICD-10-CM O99.323
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

O99.323 is a billable ICD-10-CM diagnosis code for drug use complicating pregnancy, third trimester. 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 complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 226 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 Other specified complications in pregnancy and Other specified substance-related disorders.

Code Identity

ICD-10-CM Code
O99.323
Billable Status
Yes — Valid for Submission
Code Describes
Drug use complicating pregnancy, third trimester
Short Description
Drug use complicating pregnancy, third trimester
Same as the full description in the CMS dataset.
Parent Code
O99.32
Drug use complicating pregnancy, childbirth, and the puerperium

Code Classification

ChapterO00-O9APregnancy, childbirth and the puerperium
SectionO94-O9AOther obstetric conditions, not elsewhere classified
CategoryO99Other maternal diseases classifiable elsewhere but complicating pregnancy, childbirth and the puerperium
This CodeO99.323Drug use complicating pregnancy, third trimester

Code EditsBilling

Medicare Code Editor checks that affect claim validity for O99.323.

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 O99.323: its own notes plus those printed at O99.32, O99, and Chapter 15. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From O99 Other maternal diseases classifiable elsewhere but complicating pregnancy, childbirth and the puerperium applies to 96 codes
  • conditions which complicate the pregnant state, are aggravated by the pregnancy or are a main reason for obstetric care

Excludes1

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

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 O99 Other maternal diseases classifiable elsewhere but complicating pregnancy, childbirth and the puerperium applies to 96 codes
  • when the reason for maternal care is that the condition is known or suspected to have affected the fetus (O35-O36)
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 O99.32 Drug use complicating pregnancy, childbirth, and the puerperium applies to 6 codes
  • code(s) from F11-F16 and F18-F19 to identify manifestations of the drug use
From O99 Other maternal diseases classifiable elsewhere but complicating pregnancy, childbirth and the puerperium applies to 96 codes
  • code to identify specific 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

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

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name O99.323, its category, or a range that includes it.

Excludes2 1

These codes carry an Excludes2 note naming O99.323: its condition is not part of those codes, and both may be reported when the patient has both.

  • Z79 Long term (current) drug therapy
    drug use complicating pregnancy, childbirth, and the puerperium (O99.32-) names O99.32-, which includes this code

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 MBD025
Other specified substance-related disorders
Default principal diagnosis: inpatient No · outpatient No

Patient EducationClinical

Pregnancy and Substance Use

During pregnancy, there are many things you can do to keep yourself and your baby healthy. They include getting regular prenatal care, eating healthy, and staying active. But it's also very important to avoid substances that could be harmful to you and your baby, such as tobacco, alcohol, and drugs.

Read the full article at MedlinePlus

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

Convert O99.323 to ICD-9-CMHistory

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

ICD-9-CM
648.31 Drug dependence-deliver
Approximate The match is approximate rather than exact.
ICD-9-CM
648.33 Drug dependence-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 O99.323Overview

What is the ICD-10 code for drug use complicating pregnancy, third trimester?

The ICD-10-CM code for drug use complicating pregnancy, third trimester is O99.323 (sometimes written as O99323). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is O99.323 a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report drug use complicating pregnancy, third trimester on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does O99.323 group to?

When drug use complicating pregnancy, third trimester 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 O99.323 a CC or MCC?

CMS lists O99.323 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 226 closely related codes in its exclusion list.

Who can O99.323 be reported for?

The Medicare Code Editor checks drug use complicating pregnancy, third trimester against patient demographics: this code is intended for maternity cases (age 9 through 64). Claims outside these limits are flagged as inconsistent.