2027 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 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

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 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 998. 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

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to O16.4: its own notes plus those printed at Chapter 15. A note printed at a category, block or chapter applies to every code under it.

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 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 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 O16.4, its category, or a range that includes it.

Includes 1

These notes mention O16.4.

  • O15 Eclampsia
    convulsions following conditions in O10-O14 and O16 names O16, which includes this code

Applicable To 1

These notes mention O16.4.

  • P00.0 Newborn affected by maternal hypertensive disorders
    Newborn affected by maternal conditions classifiable to O10-O11, O13-O16 names O13-O16, which includes this code

Excludes1 1

These codes carry an Excludes1 note naming O16.4: they are not reported together with it, unless the two conditions are unrelated.

  • I10 Essential (primary) hypertension
    hypertensive disease complicating pregnancy, childbirth and the puerperium (O10-O11, O13-O16) names O13-O16, which includes this code

Excludes2 2

These codes carry an Excludes2 note naming O16.4: its condition is not part of those codes, and both may be reported when the patient has both.

  • Block I10-I1A Hypertensive diseases
    hypertensive disease complicating pregnancy, childbirth and the puerperium (O10-O11, O13-O16) names O13-O16, which includes this code
  • O99.4 Diseases of the circulatory system complicating pregnancy, childbirth and the puerperium
    hypertensive disorders (O10-O16) names O10-O16, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

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 2019AddedAdded to the ICD-10-CM code setEffective October 1, 2018.
FY 2020–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About O16.4Overview

What is the ICD-10 code for unspecified maternal hypertension, complicating childbirth?

The ICD-10-CM code for unspecified maternal hypertension, complicating childbirth is O16.4 (sometimes written as O164). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

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, 2026 through September 30, 2027.

What MS-DRG does O16.4 group to?

When unspecified maternal hypertension, complicating childbirth is the principal diagnosis on an inpatient stay, it groups to MS-DRG 998 (principal Diagnosis Invalid as Discharge Diagnosis), which carries a relative weight of 0. Higher weights mean higher Medicare reimbursement.

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.