2027 ICD-10-CM Diagnosis Code O11.1Pre-existing hypertension with pre-eclampsia, first trimester
ICD-10-CM Codes›O00-O9A›O10-O16›O11
- Billable — Valid for Submission
- MCC — Major Complication or Comorbidity
- Chronic Condition
O11.1 is a billable ICD-10-CM diagnosis code for pre-existing hypertension with pre-eclampsia, first 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 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). 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
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for O11.1.
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to O11.1: 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.
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
- 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.
Use Additional Code
Add a second code, after this one, to fully describe the condition.
- code from O10 to identify the type of hypertension
- 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.
- 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 O11.1, its category, or a range that includes it.
Excludes1 2
These codes carry an Excludes1 note naming O11.1: they are not reported together with it, unless the two conditions are unrelated.
Excludes2 3
These codes carry an Excludes2 note naming O11.1: 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 puerperiumpre-existing hypertension with superimposed pre-eclampsia complicating pregnancy, childbirth and the puerperium (O11.-) names O11.-, which includes this code
- Block I10-I1A Hypertensive diseases
- O99.4 Diseases of the circulatory system complicating pregnancy, childbirth and the puerperium
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
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 O11.1 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About O11.1Overview
What is the ICD-10 code for pre-existing hypertension with pre-eclampsia, first trimester?
The ICD-10-CM code for pre-existing hypertension with pre-eclampsia, first trimester is O11.1 (sometimes written as O111). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is O11.1 (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, first trimester on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does O11.1 group to?
When pre-existing hypertension with pre-eclampsia, first 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 O11.1 a CC or MCC?
CMS lists O11.1 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 O11.1 be reported for?
The Medicare Code Editor checks pre-existing hypertension with pre-eclampsia, first trimester against patient demographics: this code is intended for maternity cases (age 9 through 64). Claims outside these limits are flagged as inconsistent.
