O35.02 vs O35.1

O35.02 (Maternal care for (suspected) central nervous system malformation or damage in fetus, anencephaly) compared with O35.1 (Maternal care for (suspected) chromosomal abnormality in fetus), from the official CMS tabular data.

Summary

These codes can be reported together when both conditions are documented, because O35.02 lists O35.1 under Excludes2, which marks them as distinct conditions.

Official rule

What is different?

Title wording.The titles share “Maternal care for (suspected)”; O35.02 says “central nervous system malformation or damage in fetus, anencephaly” where O35.1 says “chromosomal abnormality in fetus”.

Registry fact

Can these codes be reported together?

Yes, when both are documented.O35.02 lists O35.1 under Excludes2: “chromosomal abnormality in fetus (O35.1-)”. 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. O35.02 carries 1 Excludes1 note and O35.1 carries 1 Excludes1 note covering other codes; the side-by-side table quotes them.

Official rule

Is there an Excludes2 relationship?

Yes.O35.02’s tabular entry: “chromosomal abnormality in fetus (O35.1-)”. The note covers O35.1.

Official ruleGuide: Excludes1 vs Excludes2

Is one more specific?

No.Neither is a subdivision of the other, and neither title is the unspecified form; they describe different conditions within category O35.

Registry fact

Is one a parent or header code?

Both are headers.Both are non-billable headers, and neither contains the other.

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

O35.02

Maternal care for (suspected) central nervous system malformation or damage in fetus, anencephaly

↔

O35.1

Maternal care for (suspected) chromosomal abnormality in fetus

What we found

Yes, when both are documented.O35.02 carries an Excludes2 note covering O35.1: “chromosomal abnormality in fetus (O35.1-)”

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 Excludes2 Check 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

	O35.02Maternal care for (suspected) central nervous system malformation or damage in fetus, anencephaly	O35.1Maternal care for (suspected) chromosomal abnormality in fetus
Billing status	Non-billable header Report instead: O35.02X0, O35.02X1, O35.02X2, O35.02X3, O35.02X4	Non-billable header Report instead: O35.10X0, O35.10X1, O35.10X2, O35.10X3, O35.10X4
Classification	O00-O9A — Pregnancy, Childbirth and the Puerperium (O00-O9A)	O00-O9A — Pregnancy, Childbirth and the Puerperium (O00-O9A)
Definition	Maternal care for (suspected) central nervous system malformation or damage in fetus, anencephaly is a non-billable ICD-10-CM category code (O35.02).	Maternal care for (suspected) chromosomal abnormality in fetus is a non-billable ICD-10-CM category code (O35.1).
7th character	One of the following 7th characters is to be assigned to each code under category O35. 7th character 0 is for single gestations and multiple gestations where the fetus is unspecified. 7th characters 1 through 9 are for cases of multiple gestations to identify the fetus for which the code applies. The appropriate code from category O30, Multiple gestation, must also be assigned when assigning a code from category O35 that has a 7th character of 1 through 9.	One of the following 7th characters is to be assigned to each code under category O35. 7th character 0 is for single gestations and multiple gestations where the fetus is unspecified. 7th characters 1 through 9 are for cases of multiple gestations to identify the fetus for which the code applies. The appropriate code from category O30, Multiple gestation, must also be assigned when assigning a code from category O35 that has a 7th character of 1 through 9.
Includes	the listed conditions in the fetus as a reason for hospitalization or other obstetric care to the mother, or for termination of pregnancy	the listed conditions in the fetus as a reason for hospitalization or other obstetric care to the mother, or for termination of pregnancy
Excludes1	encounter for suspected maternal and fetal conditions ruled out (Z03.7-)	encounter for suspected maternal and fetal conditions ruled out (Z03.7-)
Excludes2	chromosomal abnormality in fetus (O35.1-)	—
Code also	any associated maternal condition	any associated maternal condition

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