2027 ICD-10-CM Diagnosis Code O10.42Pre-existing secondary hypertension complicating childbirth

ICD-10-CM Codes›O00-O9A›O10-O16›O10

ICD-10-CM O10.42
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

O10.42 is a billable ICD-10-CM diagnosis code for pre-existing secondary 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. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 298 closely related codes. The code is restricted by the Medicare Code Editor to maternity cases (age 9 through 64). Coders also document this condition as hypertension secondary to renal disease complicating AND/OR reason for care during childbirth. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Complications specified during childbirth, Hypertension and hypertensive-related conditions complicating pregnancy; childbirth; and the puerperium, and Hypertension with complications and secondary hypertension.

Code Identity

ICD-10-CM Code
O10.42
Billable Status
Yes — Valid for Submission
Code Describes
Pre-existing secondary hypertension complicating childbirth
Short Description
Pre-existing secondary hypertension complicating childbirth
Same as the full description in the CMS dataset.
Parent Code
O10.4
Pre-existing secondary hypertension complicating pregnancy, childbirth and the puerperium

Code Classification

ChapterO00-O9APregnancy, childbirth and the puerperium
SectionO10-O16Edema, proteinuria and hypertensive disorders in pregnancy, childbirth and the puerperium
CategoryO10Pre-existing hypertension complicating pregnancy, childbirth and the puerperium
This CodeO10.42Pre-existing secondary hypertension complicating childbirth

Code EditsBilling

Medicare Code Editor checks that affect claim validity for O10.42.

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.

  • Hypertension secondary to renal disease complicating AND/OR reason for care during childbirth
  • Hypertension secondary to renal disease in obstetric context
  • Pre-existing secondary hypertension complicating pregnancy, childbirth and puerperium

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to O10.42: its own notes plus those printed at O10.4, O10, 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 O10 Pre-existing hypertension complicating pregnancy, childbirth and the puerperium applies to 36 codes
  • pre-existing hypertension with pre-existing proteinuria complicating pregnancy, childbirth and the puerperium

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 O10 Pre-existing hypertension complicating pregnancy, childbirth and the puerperium applies to 36 codes
  • pre-existing hypertension with superimposed pre-eclampsia complicating pregnancy, childbirth and the puerperium (O11.-)
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 O10.4 Pre-existing secondary hypertension complicating pregnancy, childbirth and the puerperium applies to 6 codes
  • code from I15 to identify the type of secondary 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 O10.42, its category, or a range that includes it.

Includes 2

These notes mention O10.42.

  • O11 Pre-existing hypertension with pre-eclampsia
    conditions in O10 complicated by pre-eclampsia names O10, which includes this code
  • O15 Eclampsia
    convulsions following conditions in O10-O14 and O16 names O10-O14, which includes this code

Applicable To 1

These notes mention O10.42.

  • 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 1

These codes carry an Excludes1 note naming O10.42: 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 O10-O11, which includes this code

Excludes2 2

These codes carry an Excludes2 note naming O10.42: 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 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

Use Additional Code 1

These codes say to use an additional code from the note, and O10.42 is one of the codes named.

  • O11 Pre-existing hypertension with pre-eclampsia
    code from O10 to identify the type of hypertension names O10, 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 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

Patient EducationClinical

Childbirth Problems

Childbirth is the process of giving birth to a baby. It includes labor and delivery. Usually everything goes well, but problems can happen. They may cause a risk to the mother, baby, or both. Some of the more common childbirth problems include:

Read the full article at MedlinePlus

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

Convert O10.42 to ICD-9-CMHistory

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

ICD-9-CM
642.11 Renal hyperten pg-deliv
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 O10.42Overview

What is the ICD-10 code for pre-existing secondary hypertension complicating childbirth?

The ICD-10-CM code for pre-existing secondary hypertension complicating childbirth is O10.42 (sometimes written as O1042). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is O10.42 a billable code?

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

What MS-DRG does O10.42 group to?

When pre-existing secondary 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.

Is O10.42 a CC or MCC?

CMS lists O10.42 as an MCC (major complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 298 closely related codes in its exclusion list.

Who can O10.42 be reported for?

The Medicare Code Editor checks pre-existing secondary 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.