2027 ICD-10-CM Diagnosis Code Z3A.3535 weeks gestation of pregnancy

ICD-10-CM Codes›Z00–Z99›Z30-Z39›Z3A

ICD-10-CM Z3A.35
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

Z3A.35 is a billable ICD-10-CM diagnosis code for 35 weeks gestation of pregnancy. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 951. The code is restricted by the Medicare Code Editor to maternity cases (age 9 through 64), not accepted as a principal diagnosis, and exempt from POA reporting. Coders also document this condition as gestation period, 35 weeks. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Gestational weeks.

Code Identity

ICD-10-CM Code
Z3A.35
Billable Status
Yes — Valid for Submission
Code Describes
35 weeks gestation of pregnancy
Short Description
35 weeks gestation of pregnancy
Same as the full description in the CMS dataset.
Parent Code
Z3A.3
Weeks of gestation of pregnancy, weeks 30-39

Code Classification

ChapterZ00–Z99Factors influencing health status and contact with health services
SectionZ30-Z39Persons encountering health services in circumstances related to reproduction
CategoryZ3AWeeks of gestation
This CodeZ3A.3535 weeks gestation of pregnancy

Code EditsBilling

Medicare Code Editor checks that affect claim validity for Z3A.35.

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).
Unacceptable principal diagnosis
There are selected codes that describe a circumstance which influences an individual's health status but not a current illness or injury, or codes that are not specific manifestations but may be due to an underlying cause. These codes are considered unacceptable as a principal diagnosis.

Present on Admission (POA)Billing

Z3A.35 is exempt from POA reporting on inpatient claims to general acute care hospitals. Review the other POA exempt codes in Persons encountering health services in circumstances related to reproduction (Z30-Z39).

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Gestation period, 35 weeks
  • Third trimester pregnancy less than 36 weeks

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to Z3A.35: its own notes plus those printed at Z3A and Chapter 21. A note printed at a category, block or chapter applies to every code under it.

Code First

The underlying condition named in the note is sequenced before this code.

From Z3A Weeks of gestation applies to 38 codes

Notes

General instructions on how these codes are used.

From Z3A Weeks of gestation applies to 38 codes
  • Codes from category Z3A are for use, only on the maternal record, to indicate the weeks of gestation of the pregnancy, if known.
From Chapter 21 (Z00-Z99) Factors influencing health status and contact with health services applies to 1,425 codes
  • Z codes represent reasons for encounters. A corresponding procedure code must accompany a Z code if a procedure is performed. Categories Z00-Z99 are provided for occasions when circumstances other than a disease, injury or external cause classifiable to categories A00-Y89 are recorded as 'diagnoses' or 'problems'. This can arise in two main ways:
  • (a) When a person who may or may not be sick encounters the health services for some specific purpose, such as to receive limited care or service for a current condition, to donate an organ or tissue, to receive prophylactic vaccination (immunization), or to discuss a problem which is in itself not a disease or injury.
  • (b) When some circumstance or problem is present which influences the person's health status but is not in itself a current illness or injury.

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

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name Z3A.35, its category, or a range that includes it.

Use Additional Code 1

These codes say to use an additional code from the note, and Z3A.35 is one of the codes named.

  • Chapter 15 (O00-O9A) Pregnancy, childbirth and the puerperium
    code, if applicable, from category Z3A, Weeks of gestation, to identify the specific week of the pregnancy, if known. names Z3A, which includes this code

Notes 1

These notes mention Z3A.35.

  • Z3A Weeks of gestation
    Codes from category Z3A are for use, only on the maternal record, to indicate the weeks of gestation of the pregnancy, if known. names Z3A, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

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

CCSR PRG002
Gestational weeks
Default principal diagnosis: inpatient No · outpatient Yes

Patient EducationClinical

Pregnancy

You're going to have a baby! It's an exciting time, but it can also feel a bit overwhelming. You may have a lot of questions, including what you can do to give your baby a healthy start. Taking care of your health while you're pregnant will help your fetus develop into a healthy baby. To do that, it's important to:

Read the full article at MedlinePlus

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

Convert Z3A.35 to ICD-9-CMHistory

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

ICD-9-CM
No Map There is no ICD-9 equivalent for this code.

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 Z3A.35Overview

What is the ICD-10 code for 35 weeks gestation of pregnancy?

The ICD-10-CM code for 35 weeks gestation of pregnancy is Z3A.35 (sometimes written as Z3A35). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is Z3A.35 (Weeks of gestation of pregnancy, weeks 30-39) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report 35 weeks gestation of pregnancy on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does Z3A.35 group to?

On inpatient claims, 35 weeks gestation of pregnancy maps to MS-DRG 951 (other Factors Influencing Health Status), which carries a relative weight of 0.5574. Higher weights mean higher Medicare reimbursement.

Can Z3A.35 be a principal diagnosis?

No. The Medicare Code Editor rejects this code as a principal diagnosis because 35 weeks gestation of pregnancy describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.

Who can Z3A.35 be reported for?

The Medicare Code Editor checks 35 weeks gestation of pregnancy against patient demographics: this code is intended for maternity cases (age 9 through 64). Claims outside these limits are flagged as inconsistent.