2027 ICD-10-CM Diagnosis Code O99.352Diseases of the nervous system complicating pregnancy, second trimester

ICD-10-CM Codes›O00-O9A›O94-O9A›O99

ICD-10-CM O99.352
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

O99.352 is a billable ICD-10-CM diagnosis code for diseases of the nervous system complicating pregnancy, second trimester. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 817 through 819, 831 through 833. The code is restricted by the Medicare Code Editor to maternity cases (age 9 through 64). In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified complications in pregnancy.

Code Identity

ICD-10-CM Code
O99.352
Billable Status
Yes — Valid for Submission
Code Describes
Diseases of the nervous system complicating pregnancy, second trimester
Short Description
Diseases of the nervous sys comp pregnancy, second trimester
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 CodeO99.352Diseases of the nervous system complicating pregnancy, second trimester

Code EditsBilling

Medicare Code Editor checks that affect claim validity for O99.352.

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).

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to O99.352: its own notes plus those printed at O99.35, O99, and Chapter 15. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From O99 Other maternal diseases classifiable elsewhere but complicating pregnancy, childbirth and the puerperium applies to 96 codes
  • conditions which complicate the pregnant state, are aggravated by the pregnancy or are a main reason for obstetric care

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From Chapter 15 (O00-O9A) Pregnancy, childbirth and the puerperium applies to 2,481 codes
  • supervision of normal pregnancy (Z34.-)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From O99.35 Diseases of the nervous system complicating pregnancy, childbirth, and the puerperium applies to 6 codes
  • pregnancy related peripheral neuritis (O26.8-)
From O99 Other maternal diseases classifiable elsewhere but complicating pregnancy, childbirth and the puerperium applies to 96 codes
  • when the reason for maternal care is that the condition is known or suspected to have affected the fetus (O35-O36)
From Chapter 15 (O00-O9A) Pregnancy, childbirth and the puerperium applies to 2,481 codes
  • mental and behavioral disorders associated with the puerperium (F53.-)
  • obstetrical tetanus (A34)
  • postpartum necrosis of pituitary gland (E23.0)
  • puerperal osteomalacia (M83.0)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From O99 Other maternal diseases classifiable elsewhere but complicating pregnancy, childbirth and the puerperium applies to 96 codes
  • code to identify specific condition
From Chapter 15 (O00-O9A) Pregnancy, childbirth and the puerperium applies to 2,481 codes
  • code, if applicable, from category Z3A, Weeks of gestation, to identify the specific week of the pregnancy, if known.

Notes

General instructions on how these codes are used.

From Chapter 15 (O00-O9A) Pregnancy, childbirth and the puerperium applies to 2,481 codes
  • CODES FROM THIS CHAPTER ARE FOR USE ONLY ON MATERNAL RECORDS, NEVER ON NEWBORN RECORDS
  • Codes from this chapter are for use for conditions related to or aggravated by the pregnancy, childbirth, or by the puerperium (maternal causes or obstetric causes)
  • Trimesters are counted from the first day of the last menstrual period. They are defined as follows:
  • 1st trimester- less than 14 weeks 0 days
  • 2nd trimester- 14 weeks 0 days to less than 28 weeks 0 days
  • 3rd trimester- 28 weeks 0 days until delivery

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Clinical ClassificationClinical

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

CCSR PRG028
Other specified complications in pregnancy
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Health Problems in Pregnancy

A health problem in pregnancy is any disease or condition that could affect your health or the health of your fetus. Some health problems may make it more likely that you will have a high-risk pregnancy. A high-risk pregnancy is one in which you, your fetus, or both are at higher risk for health problems than in a typical pregnancy.

The full article covers:

  • What are health problems in pregnancy?
  • What raises my risk for health problems during pregnancy?
  • Can chronic health conditions cause problems in pregnancy?
  • Can health problems in pregnancy be prevented?

Read the full article at MedlinePlus

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

Convert O99.352 to ICD-9-CMHistory

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

ICD-9-CM
646.81 Preg compl NEC-delivered
Approximate The match is approximate rather than exact.
ICD-9-CM
646.83 Preg compl NEC-antepart
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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About O99.352Overview

Is O99.352 a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report diseases of the nervous system complicating pregnancy, second trimester on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does O99.352 group to?

When diseases of the nervous system complicating pregnancy, second trimester is the principal diagnosis on an inpatient stay, it groups to MS-DRG 833, 832, 831, 819, 818, 817, with relative weights from 0.5000 to 1.7586 depending on complications. Higher weights mean higher Medicare reimbursement.

Who can O99.352 be reported for?

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

Does O99.352 need an additional code?

When the condition applies, yes. The Use Additional Code note at O99, which applies to O99.352, reads: code to identify specific condition. The additional code is reported after O99.352.

What is the ICD-9 equivalent of O99.352?

Under the General Equivalence Mappings, diseases of the nervous system complicating pregnancy, second trimester converts to ICD-9-CM 646.81 (preg compl NEC-delivered) and 646.83 (preg compl NEC-antepart). The mapping is approximate, so confirm the match fits the documentation.