2027 ICD-10-CM Diagnosis Code O11.9Pre-existing hypertension with pre-eclampsia, unspecified trimester

ICD-10-CM Codes›O00-O9A›O10-O16›O11

ICD-10-CM O11.9
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

O11.9 is a billable ICD-10-CM diagnosis code for pre-existing hypertension with pre-eclampsia, unspecified 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. The code is restricted by the Medicare Code Editor to maternity cases (age 9 through 64). Coders also document this condition as pre-eclampsia. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Hypertension and hypertensive-related conditions complicating pregnancy; childbirth; and the puerperium and Hypertension with complications and secondary hypertension.

Code Identity

ICD-10-CM Code
O11.9
Billable Status
Yes — Valid for Submission
Code Describes
Pre-existing hypertension with pre-eclampsia, unspecified trimester
Short Description
Pre-existing hypertension with pre-eclampsia, unsp trimester
Parent Code
O11
Pre-existing hypertension with pre-eclampsia

Code Classification

ChapterO00-O9APregnancy, childbirth and the puerperium
SectionO10-O16Edema, proteinuria and hypertensive disorders in pregnancy, childbirth and the puerperium
CategoryO11Pre-existing hypertension with pre-eclampsia
This CodeO11.9Pre-existing hypertension with pre-eclampsia, unspecified trimester

Code EditsBilling

Medicare Code Editor checks that affect claim validity for O11.9.

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.

  • Pre-eclampsia
  • Pre-eclampsia added to pre-existing hypertension
  • Pre-eclampsia or eclampsia with pre-existing hypertension

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to O11.9: its own notes plus those printed at O11 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 O11 Pre-existing hypertension with pre-eclampsia applies to 6 codes
  • conditions in O10 complicated by pre-eclampsia
  • pre-eclampsia superimposed pre-existing hypertension

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 O11 Pre-existing hypertension with pre-eclampsia applies to 6 codes
  • code from O10 to identify the type of hypertension
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 O11.9, its category, or a range that includes it.

Includes 1

These notes mention O11.9.

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

Applicable To 1

These notes mention O11.9.

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

Excludes1 2

These codes carry an Excludes1 note naming O11.9: they are not reported together with it, unless the two conditions are unrelated.

  • O14 Pre-eclampsia
    pre-existing hypertension with pre-eclampsia (O11) names O11, which includes this code
  • I10 Essential (primary) hypertension
    hypertensive disease complicating pregnancy, childbirth and the puerperium (O10-O11, O13-O16) names O10-O11, which includes this code

Excludes2 3

These codes carry an Excludes2 note naming O11.9: its condition is not part of those codes, and both may be reported when the patient has both.

  • O10 Pre-existing hypertension complicating pregnancy, childbirth and the puerperium
    pre-existing hypertension with superimposed pre-eclampsia complicating pregnancy, childbirth and the puerperium (O11.-) names O11.-, which includes this code
  • Block I10-I1A Hypertensive diseases
    hypertensive disease complicating pregnancy, childbirth and the puerperium (O10-O11, O13-O16) names O10-O11, 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

Clinical ClassificationClinical

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

CCSR PRG020
Hypertension and hypertensive-related conditions complicating pregnancy; childbirth; and the puerperium
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR CIR008
Hypertension with complications and secondary hypertension
Default principal diagnosis: inpatient No · outpatient No

Clinical InformationClinical

  • Chronic Maternal Hypertension with Superimposed Preeclampsia

    chronic hypertension in association with preeclampsia.

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 O11.9 to ICD-9-CMHistory

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

ICD-9-CM
642.20 Old hyperten preg-unspec
Approximate The match is approximate rather than exact.
ICD-9-CM
642.70 Tox w old hyperten-unsp
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 O11.9Overview

What is the ICD-10 code for pre-existing hypertension with pre-eclampsia, unspecified trimester?

The ICD-10-CM code for pre-existing hypertension with pre-eclampsia, unspecified trimester is O11.9 (sometimes written as O119). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is O11.9 (Pre-existing hypertension with pre-eclampsia) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report pre-existing hypertension with pre-eclampsia, unspecified trimester on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does O11.9 group to?

When pre-existing hypertension with pre-eclampsia, unspecified 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.

Who can O11.9 be reported for?

The Medicare Code Editor checks pre-existing hypertension with pre-eclampsia, unspecified trimester against patient demographics: this code is intended for maternity cases (age 9 through 64). Claims outside these limits are flagged as inconsistent.

Does O11.9 need an additional code?

When the condition applies, yes. The Use Additional Code note at O11, which applies to O11.9, reads: code from O10 to identify the type of hypertension. The additional code is reported after O11.9.