| O91.21 | Nonpurulent mastitis associated with pregnancy | NON-BILLABLE CODE |
| O91.211 | Nonpurulent mastitis associated with pregnancy, first trimester | BILLABLE CODE |
| O91.212 | Nonpurulent mastitis associated with pregnancy, second trimester | BILLABLE CODE |
| O91.213 | Nonpurulent mastitis associated with pregnancy, third trimester | BILLABLE CODE |
| O91.219 | Nonpurulent mastitis associated with pregnancy, unspecified trimester | BILLABLE CODE |
| O91.22 | Nonpurulent mastitis associated with the puerperium | BILLABLE CODE |
| O91.23 | Nonpurulent mastitis associated with lactation | BILLABLE CODE |
