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O16.9 ICD-10-CM Code: Unspecified maternal hypertension, unspecified trimester

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Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Billable · FY2027A valid, specific ICD-10-CM code, reportable for dates of service in FY2027.

What you need to know

Source: CMS/NCHS Official ICD-10-CM tabular notes, quoted. From the CMS/NCHS tabular list for the release in force. A note the category or block publishes applies to this code too, and is marked with where it comes from.

The tabular list publishes no instructional note for this code itself.

Where it sits Source: CMS/NCHS

Under:Chapter 15: Pregnancy, Childbirth and the PuerperiumO10-O16 Edema, proteinuria and hypertensive disorders in pregnancy, childbirth and the puerperiumO16 Unspecified maternal hypertension

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Inpatient Payment Groups (MS-DRG)

Potential MS-DRG participation — not a DRG assignment.

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v44, Appendix B.

  • MS-DRG 817 — OTHER ANTEPARTUM DIAGNOSES WITH O.R. PROCEDURES WITH MCC (MDC 14)
  • MS-DRG 818 — OTHER ANTEPARTUM DIAGNOSES WITH O.R. PROCEDURES WITH CC (MDC 14)
  • MS-DRG 819 — OTHER ANTEPARTUM DIAGNOSES WITH O.R. PROCEDURES WITHOUT CC/MCC (MDC 14)
  • MS-DRG 831 — OTHER ANTEPARTUM DIAGNOSES WITHOUT O.R. PROCEDURES WITH MCC (MDC 14)
  • MS-DRG 832 — OTHER ANTEPARTUM DIAGNOSES WITHOUT O.R. PROCEDURES WITH CC (MDC 14)
  • MS-DRG 833 — OTHER ANTEPARTUM DIAGNOSES WITHOUT O.R. PROCEDURES WITHOUT CC/MCC (MDC 14)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Coder workflow for O16.9

MedCoder structured workflow — derived from this code’s own official record

Before you code O16.9

  1. Unspecified does not mean incorrect. When the record gives no greater specificity, O16.9 may be the appropriate code. No code beside it in this subcategory is more specific; when the record documents what the title leaves unspecified, look the documented term up in the Alphabetic Index, which may lead to a code outside this subcategory. An unspecified code is for records that do not provide the detail a more specific code needs; a query, not an assumption, is the route to specificity (Guidelines I.A.9.b, I.B.18, I.B.1).

    See the relationships section · Guide: Other vs unspecified (NEC vs NOS) →

  2. Confirm the condition is documented as complicating the pregnancy, childbirth, or the puerperium, and check the trimester where the code carries one and the fetus character where the category requires it. Chapter 15 codes belong on the maternal record only and take sequencing priority over codes from other chapters. It is the provider’s responsibility to state that a condition is not affecting the pregnancy; the trimester is assigned from the documentation (Guidelines I.C.15.a, I.C.15.a.1, I.C.15.a.3).

    Guide: How to choose an ICD-10-CM code →

Choose the right path

  1. Does the record document the detail this title leaves unspecified?
    Yes → Look the documented term up in the Alphabetic Index; the code it leads to may sit outside this subcategory.
    No → Continue — O16.9 is appropriate when the documentation goes no further.

Consider O16.9. Then confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement
Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).
Trimester
Assigned from the documented trimester at the encounter, or the trimester in which the condition developed for inpatient stays (Guidelines I.C.15.a.3).
Any detail beyond this code’s title
What the record states that a more specific code would capture — or its absence, which itself supports the unspecified code.

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Documentation: The provider documents the condition in the terms of this code’s title and records no further detail.

Coding question: Is a more specific code supportable?

Path: No sibling in this subcategory is more specific; look the documented detail up in the Alphabetic Index.

Reason: A more specific code needs documentation of the distinguishing element; without it the unspecified code is appropriate, and a provider query is the route to specificity (Guidelines I.A.9.b, I.B.18).

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Coding context

Guidelines, coding notes, decision aids, relationships (with MS-DRG and CCSR classification), hierarchy, HCC, coverage and the context map: what a coder reaches for after the core. Each section names whether it is official source data, a MedCoder-derived relationship or MedCoder editorial.

Code Overview

Unspecified maternal hypertension, unspecified trimester is a billable ICD-10-CM diagnosis code (O16.9).

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Verify Before Coding

  • Age-restricted: the Medicare Code Editor lists this as a maternity (age 9-64) diagnosis; other ages are presumed incorrect.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder-derived relationships — computed from published CMS and AHRQ datasets

Other codes that name O16.9 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 1 Excludes1 note: I10 — Essential (primary) hypertension (via O16.-).

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Referenced by 8 Excludes2 notes across 2 chapters: I10-I1A — Hypertensive diseases (I10-I1A) (via O16.-), I11 — Hypertensive heart disease (via O16.-), I12 — Hypertensive chronic kidney disease (via O16.-), I13 — Hypertensive heart and chronic kidney disease (via O16.-), I15 — Secondary hypertension (via O16.-), I16 — Hypertensive crisis (via O16.-), I1A — Other hypertension (via O16.-), O99.4 — Diseases of the circulatory system complicating pregnancy, childbirth and the puerperium (via O16.-).

These codes’ tabular lists name this diagnosis as distinct — both may be reported when both are documented.

MS-DRG Grouper Relationships (FY2027)

Potential MS-DRG participation — not a DRG assignment.

FY2027 MS-DRG: not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity for that release.

Named in the grouper logic of 6 MS-DRGs: DRG 817 (MDC 14), DRG 818 (MDC 14), DRG 819 (MDC 14), DRG 831 (MDC 14), DRG 832 (MDC 14), DRG 833 (MDC 14).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):PRG020 — Hypertension and hypertensive-related conditions complicating pregnancy; childbirth; and the puerperium (default); CIR007 — Essential hypertension.

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical categories (Hypertension and hypertensive-related conditions complicating pregnancy; childbirth; and the puerperium, Essential hypertension).

O14.22 — HELLP syndrome (HELLP), second trimester, O14.23 — HELLP syndrome (HELLP), third trimester, O14.24 — HELLP syndrome, complicating childbirth, O14.25 — HELLP syndrome, complicating the puerperium, O14.90 — Unspecified pre-eclampsia, unspecified trimester, O14.92 — Unspecified pre-eclampsia, second trimester, O14.93 — Unspecified pre-eclampsia, third trimester, O14.94 — Unspecified pre-eclampsia, complicating childbirth, O14.95 — Unspecified pre-eclampsia, complicating the puerperium, O15.00 — Eclampsia complicating pregnancy, unspecified trimester, O15.02 — Eclampsia complicating pregnancy, second trimester, O15.03 — Eclampsia complicating pregnancy, third trimester, O15.1 — Eclampsia complicating labor, O15.2 — Eclampsia complicating the puerperium, O15.9 — Eclampsia, unspecified as to time period, O16.1 — Unspecified maternal hypertension, first trimester, O16.2 — Unspecified maternal hypertension, second trimester, O16.3 — Unspecified maternal hypertension, third trimester, O16.4 — Unspecified maternal hypertension, complicating childbirth, O16.5 — Unspecified maternal hypertension, complicating the puerperium, +60 more

Lab tests where this diagnosis supports Medicare coverage (NCD)

Medicare's National Coverage Determination (NCD) program lists this diagnosis as medical justification for these lab tests.

Partial Thromboplastin Time (PTT) Test, Pregnancy Test, Prothrombin Time Test and INR (PT/INR)

Contextual Map

Every relationship of O16.9 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run O16.9 with these 9 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes

  • I10 — Essential (primary) hypertension[Excludes1](via O16.-): “hypertensive disease complicating pregnancy, childbirth and the puerperium (O10-O11, O13-O16)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027

Referenced by Excludes2 notes

  • I10-I1A — Hypertensive diseases (I10-I1A)[Excludes2](via O16.-): “hypertensive disease complicating pregnancy, childbirth and the puerperium (O10-O11, O13-O16)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027
  • I11 — Hypertensive heart disease[Excludes2](via O16.-): “hypertensive disease complicating pregnancy, childbirth and the puerperium (O10-O11, O13-O16)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027
  • I12 — Hypertensive chronic kidney disease[Excludes2](via O16.-): “hypertensive disease complicating pregnancy, childbirth and the puerperium (O10-O11, O13-O16)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027
  • I13 — Hypertensive heart and chronic kidney disease[Excludes2](via O16.-): “hypertensive disease complicating pregnancy, childbirth and the puerperium (O10-O11, O13-O16)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027
  • I15 — Secondary hypertension[Excludes2](via O16.-): “hypertensive disease complicating pregnancy, childbirth and the puerperium (O10-O11, O13-O16)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027
  • I16 — Hypertensive crisis[Excludes2](via O16.-): “hypertensive disease complicating pregnancy, childbirth and the puerperium (O10-O11, O13-O16)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027
  • I1A — Other hypertension[Excludes2](via O16.-): “hypertensive disease complicating pregnancy, childbirth and the puerperium (O10-O11, O13-O16)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027
  • O99.4 — Diseases of the circulatory system complicating pregnancy, childbirth and the puerperium[Excludes2](via O16.-): “hypertensive disorders (O10-O16)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027

Clinical classification (CCSR)

MS-DRG Grouper

MDC crossing

  • MDC 14 — Pregnancy, Childbirth and the Puerperium[MDC crossing]: “Pregnancy, Childbirth and the Puerperium — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 94 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2027

Nearest codes

Change history

  • FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Reference

Index terms and tables, published questions and FAQ, every source behind this page with its release and checksum, the date-of-service check and the complete change history.

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2027 tabular list, index and tables, effective October 1, 2026 Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v44.0 (October 2026) Release, file and checksum · Publisher’s page
Inpatient payment groups Official source data
CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v44 Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder-derived relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder editorial explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Current data releases:ICD-10-CM FY2027 · ICD-10-PCS FY2027 · HCPCS October 2026 · MS-DRG v44 · Medicare Code Editor v44.0 · NCCI PTP Q4 2026 · MUE Q4 2026 · NCD code lists 2026-01 · LCD export September 28, 2026 · All releases and sources

Labels on this page: Official source data · MedCoder-derived relationship · MedCoder editorial explanation. How to read the labels · All data sources and release dates · CMS coding rules

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "O16.9 — Unspecified maternal hypertension, unspecified trimester." ICD-10-CM FY2027. https://medcoder.ai/icd10/code/o16.9-unspecified-maternal-hypertension-unspecified-trimester

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Unspecified maternal hypertension, unspecified trimester

No changes since FY2016 — additions, deletions, description changes and billable-status changes are tracked through FY2027, and none are recorded for this code. Note changes are tracked from FY2027 only.

Nearest Codes in This Family

Official ICD-10-CM classifications closest to O16.9 in its code family, with their registry titles.

View all codes in the O16 family