O24.312 Unspecified pre-existing diabetes mellitus in pregnancy, second trimester

Billable ICD-10-CM code, FY2026. Acts as a Complication or Comorbidity (CC) as a secondary diagnosis.

Applies from O24.3 Unspecified pre-existing diabetes mellitus in pregnancy, childbirth and the puerperium

Use additional code

• code (for):
• from category E11 to further identify any manifestation
• injectable non-insulin antidiabetic drugs (Z79.85)
• long-term (current) use of insulin (Z79.4)

MS-DRG index

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

Approximate ICD-9-CM (GEMs)

• 648.01 Diabetes mellitus of mother, complicating pregnancy, childbirth, or the puerperium, delivered, with or without mention of antepartum condition (approximate)
• 648.03 Diabetes mellitus of mother, complicating pregnancy, childbirth, or the puerperium, 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 O24.312

Back-references to O24

• Type 2 Excludes: O99.2 Endocrine, nutritional and metabolic diseases complicating pregnancy, childbirth and the puerperium ("diabetes mellitus (O24.-)")
• Type 1 Excludes: R73 Elevated blood glucose level ("diabetes mellitus in pregnancy, childbirth and the puerperium (O24.-)")

Nearby codes

• O24.12 Pre-existing type 2 diabetes mellitus, in childbirth
• O24.13 Pre-existing type 2 diabetes mellitus, in the puerperium
• O24.3 Unspecified pre-existing diabetes mellitus in pregnancy, childbirth and the puerperium
• O24.31 Unspecified pre-existing diabetes mellitus in pregnancy
• O24.311 Unspecified pre-existing diabetes mellitus in pregnancy, first trimester
• O24.312 Unspecified pre-existing diabetes mellitus in pregnancy, second trimester (this code)
• O24.313 Unspecified pre-existing diabetes mellitus in pregnancy, third trimester
• O24.319 Unspecified pre-existing diabetes mellitus in pregnancy, unspecified trimester
• O24.32 Unspecified pre-existing diabetes mellitus in childbirth
• O24.33 Unspecified pre-existing diabetes mellitus in the puerperium
• O24.4 Gestational diabetes mellitus