O91.21 – Nonpurulent mastitis associated with pregnancy

ICD-10-CM 2027 diagnosis code · Complications predominantly related to the puerperium

Non-billable header

ICD-10-CM code O91.21

Code: O91.21 (claims format: O9121)
Description: Nonpurulent mastitis associated with pregnancy
Billable: No – use a more specific code below
Valid for: Dates of service October 1, 2026 – September 30, 2027 (FY2027)
Chapter: 15. Pregnancy, childbirth and the puerperium (O00-O9A)
Block: O85-O92 Complications predominantly related to the puerperium
Parent codes: O91 › O91.2

Billable codes under O91.21

O91.21 is a header code and cannot be used on claims. Choose the most specific code:

Notes for O91.21

Applicable to:

Gestational interstitial mastitis
Gestational lymphangitis of breast
Gestational mastitis NOS
Gestational parenchymatous mastitis

Notes inherited from parent codes

Instructional notes at a category or block level apply to every code below it.

O91 – Infections of breast associated with pregnancy, the puerperium and lactation

Use additional code:

code to identify infection

Block O85-O92

Excludes2 (not included here):

mental and behavioral disorders associated with the puerperium (F53.-)
obstetrical tetanus (A34)
puerperal osteomalacia (M83.0)

Index terms for O91.21

Entries in the ICD-10-CM alphabetic index that lead to this code:

Mastitis, obstetric, associated with, pregnancy

Related codes in O91.2

Frequently asked questions

What is ICD-10 code O91.21?

O91.21 is the ICD-10-CM code for nonpurulent mastitis associated with pregnancy, in the block O85-O92 (Complications predominantly related to the puerperium).

Is O91.21 a billable code?

No. O91.21 is a header code with more specific child codes; report one of the billable codes listed above.

What category does O91.21 belong to?

It belongs to category O91 – Infections of breast associated with pregnancy, the puerperium and lactation.

Source: CDC/NCHS ICD-10-CM FY2027 code files, tabular list and index. Reference only – code assignment must follow the official ICD-10-CM guidelines and documentation in the medical record.