Excludes1 pair

O9A- vs Z33.1

O9A and Z33.1 are not coded together. ICD-10-CM declares them mutually exclusive with an Excludes1 note — the two conditions are not expected to occur together, so exactly one of them is normally correct for a given encounter. The Official Guidelines carve out one exception: if the two conditions are clearly unrelated to each other, both may be reported.

The official note, declared on Z33.1

complications of pregnancy (O00-O9A)

O9A

Maternal malignant neoplasms, traumatic injuries and abuse classifiable elsewhere but complicating pregnancy, childbirth and the puerperium

Not billable

Chapter 15: Pregnancy, childbirth and the puerperium
Section: O94-O9A

Z33.1

Pregnant state, incidental

Billable

Chapter 21: Factors influencing health status and contact with health services
Section: Z30-Z39

Use when the record says

Pregnancy NOS
Pregnant state NOS

Indexed under

Pregnancy (single) (uterine)
Carrier of › gestational, pregnant
Pregnancy › incidental finding
Status › pregnancy, incidental
State › pregnant › incidental

These two codes sit in different chapters of the Tabular List, which is usually the clearest signal that they describe different underlying processes rather than different degrees of the same one.

Excludes1 is not always absolute: where two conditions covered by the note are genuinely unrelated, CMS guidance permits reporting both. Document the reasoning rather than assuming it. More on Excludes1 vs Excludes2 · FY2027