2026 ICD-10-CM Diagnosis Code O43.021Fetus-to-fetus placental transfusion syndrome, first trimester

ICD-10-CM Codes›O00-O9A›O30-O48›O43

ICD-10-CM O43.021
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

O43.021 is a billable ICD-10-CM diagnosis code for fetus-to-fetus placental transfusion syndrome, first trimester. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) 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 Maternal care related to disorders of the placenta and placental implantation.

Code Identity

ICD-10-CM Code
O43.021
Billable Status
Yes — Valid for Submission
Code Describes
Fetus-to-fetus placental transfusion syndrome, first trimester
Short Description
Fetus-to-fetus placental transfuse syndrome, first trimester
Parent Code
O43.02
Fetus-to-fetus placental transfusion syndrome

Code Classification

ChapterO00-O9APregnancy, childbirth and the puerperium
SectionO30-O48Maternal care related to the fetus and amniotic cavity and possible delivery problems
CategoryO43Placental disorders
This CodeO43.021Fetus-to-fetus placental transfusion syndrome, first trimester

Code EditsBilling

Medicare Code Editor checks that affect claim validity for O43.021.

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).

Clinical ClassificationClinical

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

CCSR PRG018
Maternal care related to disorders of the placenta and placental implantation
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Blood Disorders

Your blood is living tissue made up of liquid and solids. The liquid part, called plasma, is made of water, salts and protein. Over half of your blood is plasma. The solid part of your blood contains red blood cells, white blood cells and platelets.

Read the full article at MedlinePlus

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

Convert O43.021 to ICD-9-CMHistory

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

ICD-9-CM
656.71 Oth placent cond-deliver
Approximate The match is approximate rather than exact.
ICD-9-CM
656.73 Oth placent cond-antepar
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 O43.021Overview

Is O43.021 (Fetus-to-fetus placental transfusion syndrome) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report fetus-to-fetus placental transfusion syndrome, first trimester on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does O43.021 group to?

When fetus-to-fetus placental transfusion syndrome, first trimester is the principal diagnosis on an inpatient stay, it groups to MS-DRG 817, 818, 819, 831, 832, 833, with relative weights from 0.5229 to 1.6880 depending on complications. Higher weights mean higher Medicare reimbursement.

Who can O43.021 be reported for?

The Medicare Code Editor checks fetus-to-fetus placental transfusion syndrome, first trimester 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 O43.021?

Under the General Equivalence Mappings, fetus-to-fetus placental transfusion syndrome, first trimester converts to ICD-9-CM 656.71 (oth placent cond-deliver) and 656.73 (oth placent cond-antepar). 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.