2026 ICD-10-CM Diagnosis Code O16.4Unspecified maternal hypertension, complicating childbirth

ICD-10-CM Codes›O00-O9A›O10-O16›O16

ICD-10-CM O16.4
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

O16.4 is a billable ICD-10-CM diagnosis code for unspecified maternal hypertension, complicating childbirth. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). The code is restricted by the Medicare Code Editor to maternity cases (age 9 through 64). Coders also document this condition as chronic hypertension complicating AND/OR reason for care during childbirth. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Complications specified during childbirth, Essential hypertension, and Hypertension and hypertensive-related conditions complicating pregnancy; childbirth; and the puerperium.

Code Identity

ICD-10-CM Code
O16.4
Billable Status
Yes — Valid for Submission
Code Describes
Unspecified maternal hypertension, complicating childbirth
Short Description
Unspecified maternal hypertension, complicating childbirth
Same as the full description in the CMS dataset.
Parent Code
O16
Unspecified maternal hypertension

Code Classification

ChapterO00-O9APregnancy, childbirth and the puerperium
SectionO10-O16Edema, proteinuria and hypertensive disorders in pregnancy, childbirth and the puerperium
CategoryO16Unspecified maternal hypertension
This CodeO16.4Unspecified maternal hypertension, complicating childbirth

Code EditsBilling

Medicare Code Editor checks that affect claim validity for O16.4.

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).

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Chronic hypertension complicating AND/OR reason for care during childbirth
  • Chronic hypertension in obstetric context
  • Hypertension complicating pregnancy, childbirth and the puerperium
  • Hypertension complicating pregnancy, childbirth and the puerperium, antepartum

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Hypertension, hypertensive(accelerated) (benign) (essential) (idiopathic) (malignant) (systemic)
      • complicating
        • childbirth (labor)

Clinical ClassificationClinical

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

CCSR PRG023
Complications specified during childbirth
Default principal diagnosis: inpatient No · outpatient No
CCSR CIR007
Essential hypertension
Default principal diagnosis: inpatient No · outpatient No
CCSR PRG020
Hypertension and hypertensive-related conditions complicating pregnancy; childbirth; and the puerperium
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

High Blood Pressure in Pregnancy

Blood pressure is the force of your blood pushing against the walls of your arteries. Your arteries are blood vessels that carry blood from your heart to other parts of your body. High blood pressure, or hypertension, is blood pressure that is higher than normal.

The full article covers:

  • What is high blood pressure in pregnancy?
  • What are the types of high blood pressure in pregnancy?
  • Who is more likely to develop high blood pressure in pregnancy?
  • What are the symptoms of high blood pressure in pregnancy?
  • What problems can high blood pressure in pregnancy cause?
  • How is high blood pressure in pregnancy diagnosed?
  • What are the treatments for high blood pressure in pregnancy?

Read the full article at MedlinePlus

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

Convert O16.4 to ICD-9-CMHistory

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

ICD-9-CM
642.91 Hypertens NOS-delivered
Approximate The match is approximate rather than exact.

Code History & ChangesHistory

Replacement O16.4 replaces the following previously assigned code(s):

  • O16.9 - Unspecified maternal hypertension, unspecified trimester
FY 2018AddedAdded to the ICD-10-CM code setEffective October 1, 2017.
FY 2019–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About O16.4Overview

Is O16.4 (Unspecified maternal hypertension) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report unspecified maternal hypertension, complicating childbirth on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Who can O16.4 be reported for?

The Medicare Code Editor checks unspecified maternal hypertension, complicating childbirth 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 O16.4?

Under the General Equivalence Mappings, unspecified maternal hypertension, complicating childbirth converts to ICD-9-CM 642.91 (hypertens NOS-delivered). 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.