O91.22
Nonpurulent mastitis associated with the puerperium
O91.22 (also written O9122) is a billable ICD-10-CM diagnosis code for nonpurulent mastitis associated with the puerperium. It is part of the FY2027 code set, effective October 1, 2026. It is one of the 18 codes in category O91 (Infections of breast associated with pregnancy, the puerperium and lactation). The Alphabetic Index lists it under 6 entries. Its coding notes include a Use additional code instruction, 1 Excludes1 entry and 7 Excludes2 entries.
Guidelines tip
From the FY2027 Official Guidelines. ICD10Ref adds no rules of its own.
The trimester character comes from the provider's documentation for the current encounter. The unspecified trimester code should rarely be used.
Use additional code
Add the listed code as a secondary code, if known.
- code to identify infection
Also from chapter/block level (1 note)
- code, if applicable, from category Z3A, Weeks of gestation, to identify the specific week of the pregnancy, if known.
Excludes1
Not coded here. The listed conditions generally should not be reported together.
Also from chapter/block level (1 note)
- supervision of normal pregnancy (Z34.-)
Excludes2
Not included here. Both codes may be reported if the patient has both conditions.
Also from chapter/block level (7 notes)
Care settings
How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.
Home Health Primary
Accepted as the primary (principal) diagnosis on a home health claim. The Home Health Grouper assigns it to the MMTA - Other clinical group.
Source: CMS Home Health Grouper Software v07.2.26, effective October 1, 2026Inclusion terms
Conditions classified to this code.
- Puerperal interstitial mastitis
- Puerperal lymphangitis of breast
- Puerperal mastitis NOS
- Puerperal parenchymatous mastitis
Notes
Also from chapter/block level (6 notes)
- 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
Alphabetic Index terms
Terms the official Alphabetic Index lists for this code. 6 entries
- Lymphadenitis, breast, puerperal, postpartum (nonpurulent)
- Mastitis (acute) (diffuse) (nonpuerperal) (subacute), obstetric (interstitial) (nonpurulent), associated with, puerperium
- Puerperal, puerperium (complicated by, complications), galactophoritis
- Puerperal, puerperium (complicated by, complications), lymphangitis, breast
- Puerperal, puerperium (complicated by, complications), mammitis
- Puerperal, puerperium (complicated by, complications), mastitis