O91.211 Nonpurulent mastitis associated with pregnancy, first trimester

Billable ICD-10-CM code, FY2026.

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

Use additional code

• code to identify infection

Applies from O91.21 Nonpurulent mastitis associated with pregnancy

Applicable to

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

MS-DRG index

Defines the logic of DRG(s) 817-819 in MDC 14.

Approximate ICD-9-CM (GEMs)

• 675.21 Nonpurulent mastitis associated with childbirth, delivered, with or without mention of antepartum condition (approximate)
• 675.23 Nonpurulent mastitis associated with childbirth, antepartum condition or complication (approximate)

Medicare Code Edits (MCE v43.1 (April 2026))

• Maternity diagnoses (age 9 through 64): Age conflict edit. These diagnoses are clinically expected only in patients age 9 through 64.

Code annotations containing back-references to O91.211

Back-references to O91.2

• Type 2 Excludes: L03.31 Cellulitis of trunk ("puerperal cellulitis of breast (O91.2)")

Back-references to O91

• Type 1 Excludes: N61 Inflammatory disorders of breast ("inflammatory disorder of breast associated with childbirth (O91.-)")

Nearby codes

• O91.119 Abscess of breast associated with pregnancy, unspecified trimester
• O91.12 Abscess of breast associated with the puerperium
• O91.13 Abscess of breast associated with lactation
• O91.2 Nonpurulent mastitis associated with pregnancy, the puerperium and lactation
• O91.21 Nonpurulent mastitis associated with pregnancy
• O91.211 Nonpurulent mastitis associated with pregnancy, first trimester (this code)
• O91.212 Nonpurulent mastitis associated with pregnancy, second trimester
• O91.213 Nonpurulent mastitis associated with pregnancy, third trimester
• O91.219 Nonpurulent mastitis associated with pregnancy, unspecified trimester
• O91.22 Nonpurulent mastitis associated with the puerperium
• O91.23 Nonpurulent mastitis associated with lactation