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O28 vs R79.1

O28 (Abnormal findings on antenatal screening of mother) compared with R79.1 (Abnormal coagulation profile), from the official CMS tabular data.

Summary

These codes can be reported together when both conditions are documented, because R79.1 lists O28 under Excludes2, which marks them as distinct conditions.

Official rule
What is different?

The conditions named, billing status and chapter.O28 is “Abnormal findings on antenatal screening of mother”; R79.1 is “Abnormal coagulation profile”. O28 is a non-billable header; R79.1 is billable. O28 sits in O00-O9A — Pregnancy, Childbirth and the Puerperium (O00-O9A); R79.1 in R00-R99 — Symptoms, Signs and Abnormal Clinical and Laboratory Findings, Not Elsewhere Classified (R00-R99).

Registry fact

Can these codes be reported together?

Yes, when both are documented.R79.1 lists O28 under Excludes2: “abnormal findings on antenatal screening of mother (O28.-)”. Excludes2 marks distinct conditions that may both be reported when both are documented.

Official ruleGuide: Excludes1 vs Excludes2

Is there an Excludes1 relationship?

None.Neither entry carries an Excludes1 note that names the other code. O28 carries 1 Excludes1 note and R79.1 carries 7 Excludes1 notes covering other codes; the side-by-side table quotes them.

Official rule

Is there an Excludes2 relationship?

Yes.R79.1’s tabular entry: “abnormal findings on antenatal screening of mother (O28.-)”. The note covers O28.

Official ruleGuide: Excludes1 vs Excludes2

Is one more specific?

Not comparable.The codes sit in different categories; specificity is only comparable within one category.

Is one a parent or header code?

One is a header.O28 is a non-billable header, but R79.1 is not one of its subdivisions.

Registry fact

Are there sequencing instructions?

None.Neither entry carries a Code First or Use Additional Code note that names the other.

Official rule

Are there other coding relationships?

None found.No laterality, encounter-phase, Table of Neoplasms, Table of Drugs and Chemicals, or history-versus-active-disease relationship links these codes.

MedCoder-derived

Official rule: a tabular instructional note or a section of the ICD-10-CM Official Guidelines, quoted as published. Registry fact: the codes’ own published attributes (titles, billable status, position in the hierarchy, code set). MedCoder-derived: a reading MedCoder computes from those facts; it is not itself a rule. How to read the labels

Can these codes be reported together?

Informational

Excludes2 relationship

R79.1
Abnormal coagulation profile
↔
O28
Abnormal findings on antenatal screening of mother

What we found

Yes, when both are documented.R79.1 carries an Excludes2 note covering O28: “abnormal findings on antenatal screening of mother (O28.-)”

Excludes2 marks distinct conditions — both may be reported when both are documented.

What to review

Report both only when the documentation supports both conditions; otherwise report the one documented.

Guide: Excludes1 vs Excludes2Check these on a claim

Why it matters

An Excludes2 note means the excluded condition is not part of the code above it, but a patient can have both. Report both when both are documented.

Source / rule

CMS ICD-10-CM tabular instructional notes

Official guidance behind these answers

  • Section I.A.12.b — Excludes2 · applies to: Excludes2

    A type 2 Excludes note represents “Not included here.” An excludes2 note indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.

    ICD-10-CM Official Guidelines FY2026

Quoted from the ICD-10-CM Official Guidelines for Coding and Reporting in effect for the release shown. The tabular notes above are the code-level instruction; these sections are the convention that says how such a note is applied. Source document (CMS PDF) · Release and checksum

Side by side

O28Abnormal findings on antenatal screening of motherR79.1Abnormal coagulation profile
Billing statusNon-billable header

Report instead: O28.0, O28.1, O28.2, O28.3, O28.4

Billable
ClassificationO00-O9A — Pregnancy, Childbirth and the Puerperium (O00-O9A)R00-R99 — Symptoms, Signs and Abnormal Clinical and Laboratory Findings, Not Elsewhere Classified (R00-R99)
DefinitionAbnormal findings on antenatal screening of mother is a non-billable ICD-10-CM category code (O28).Abnormal coagulation profile is a billable ICD-10-CM diagnosis code (R79.1).
Includes—
Abnormal or prolonged bleeding time
Abnormal or prolonged coagulation time
Abnormal or prolonged partial thromboplastin time [PTT]
Abnormal or prolonged prothrombin time [PT]
Excludes1
diagnostic findings classified elsewhere - see Alphabetical Index
coagulation defects (D68.-)
asymptomatic hyperuricemia (E79.0)
hypoglycemia NOS (E16.2)
neonatal hypoglycemia (P70.3-P70.4)
specific findings indicating disorder of amino-acid metabolism (E70-E72)
specific findings indicating disorder of carbohydrate metabolism (E73-E74)
specific findings indicating disorder of lipid metabolism (E75.-)
Excludes2
maternal care related to the fetus and amniotic cavity and possible delivery problems (O30-O48)
maternal diseases classifiable elsewhere but complicating pregnancy, labor and delivery, and the puerperium (O98-O99)
abnormality of fluid, electrolyte or acid-base balance (E86-E87)
hyperglycemia NOS (R73.9)
abnormal findings on antenatal screening of mother (O28.-)
abnormalities of lipids (E78.-)
abnormalities of platelets and thrombocytes (D69.-)
abnormalities of white blood cells classified elsewhere (D70-D72)
coagulation hemorrhagic disorders (D65-D68)
diagnostic abnormal findings classified elsewhere - see Alphabetical Index
hemorrhagic and hematological disorders of newborn (P50-P61)
Use additional code—
code to identify any retained foreign body, if applicable (Z18.-)

Notes are the code’s own tabular entry, quoted as published. A note that names the other code is the one the verdict above rests on.

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Derived from the official CMS ICD-10-CM tabular data (FY2027). A coding-rule comparison, not billing advice: payer-specific edits and medical-necessity policy are outside its scope. All data sources