2026 ICD-10-CM Diagnosis Code O99.355Diseases of the nervous system complicating the puerperium

ICD-10-CM Codes›O00-O9A›O94-O9A›O99

ICD-10-CM O99.355
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

O99.355 is a billable ICD-10-CM diagnosis code for diseases of the nervous system complicating the puerperium. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). The code is restricted by the Medicare Code Editor to maternity cases (age 9 through 64). Coders also document this condition as maternal epilepsy due to perinatal stroke. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Complications specified during the puerperium.

Code Identity

ICD-10-CM Code
O99.355
Billable Status
Yes — Valid for Submission
Code Describes
Diseases of the nervous system complicating the puerperium
Short Description
Diseases of the nervous system complicating the puerperium
Same as the full description in the CMS dataset.
Parent Code
O99.35
Diseases of the nervous system complicating pregnancy, childbirth, and the puerperium

Code Classification

ChapterO00-O9APregnancy, childbirth and the puerperium
SectionO94-O9AOther obstetric conditions, not elsewhere classified
CategoryO99Other maternal diseases classifiable elsewhere but complicating pregnancy, childbirth and the puerperium
This CodeO99.355Diseases of the nervous system complicating the puerperium

Code EditsBilling

Medicare Code Editor checks that affect claim validity for O99.355.

Maternity diagnoses
The Medicare Code Editor detects inconsistencies in maternity cases by checking a patient's age and any diagnosis on the patient's record. The maternity code edits apply to patients age ange is 9–64 years inclusive (e.g., diabetes in pregnancy, antepartum pulmonary complication).

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Maternal epilepsy due to perinatal stroke
  • Post-cerebrovascular accident epilepsy
  • Posttraumatic seizure

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Puerperal, puerperium(complicated by, complications)
      • hemiplegia, cerebral
    • Puerperal, puerperium(complicated by, complications)
      • nervous system disorder

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR PRG027
Complications specified during the puerperium
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Neurologic Diseases

The brain, spinal cord, and nerves make up the nervous system. Together they control all the workings of the body. When something goes wrong with a part of your nervous system, you can have trouble moving, speaking, swallowing, breathing, or learning. You can also have problems with your memory, senses, or mood.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert O99.355 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
646.82 Preg compl NEC-del w p/p
Approximate The match is approximate rather than exact.
ICD-9-CM
646.84 Preg compl NEC-postpart
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About O99.355Overview

Is O99.355 a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report diseases of the nervous system complicating the puerperium on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Who can O99.355 be reported for?

The Medicare Code Editor checks diseases of the nervous system complicating the puerperium against patient demographics: this code is intended for maternity cases (age 9 through 64). Claims outside these limits are flagged as inconsistent.

What is the ICD-9 equivalent of O99.355?

Under the General Equivalence Mappings, diseases of the nervous system complicating the puerperium converts to ICD-9-CM 646.82 (preg compl NEC-del w p/p) and 646.84 (preg compl NEC-postpart). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.