O99.351 Diseases of the nervous system complicating pregnancy, first trimester

Billable ICD-10-CM code, FY2026.

Applies from O99 Other maternal diseases classifiable elsewhere but complicating pregnancy, childbirth and the puerperium

Includes

• conditions which complicate the pregnant state, are aggravated by the pregnancy or are a main reason for obstetric care

Excludes2 (not included here)

• when the reason for maternal care is that the condition is known or suspected to have affected the fetus (O35-O36)

Use additional code

• code to identify specific condition

Applies from O99.35 Diseases of the nervous system complicating pregnancy, childbirth, and the puerperium

Applicable to

• Conditions in G00-G99

Excludes2 (not included here)

• pregnancy related peripheral neuritis (O26.8-)

MS-DRG index

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

Approximate ICD-9-CM (GEMs)

• 646.81 Other specified complications of pregnancy, delivered, with or without mention of antepartum condition (approximate)
• 646.83 Other specified complications of pregnancy, 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.

Nearby codes

• O99.343 Other mental disorders complicating pregnancy, third trimester
• O99.344 Other mental disorders complicating childbirth
• O99.345 Other mental disorders complicating the puerperium
• O99.35 Diseases of the nervous system complicating pregnancy, childbirth, and the puerperium
• O99.350 Diseases of the nervous system complicating pregnancy, unspecified trimester
• O99.351 Diseases of the nervous system complicating pregnancy, first trimester (this code)
• O99.352 Diseases of the nervous system complicating pregnancy, second trimester
• O99.353 Diseases of the nervous system complicating pregnancy, third trimester
• O99.354 Diseases of the nervous system complicating childbirth
• O99.355 Diseases of the nervous system complicating the puerperium
• O99.4 Diseases of the circulatory system complicating pregnancy, childbirth and the puerperium