ICD-10-CM 2027 diagnosis code
O43.021Fetus-to-fetus placental transfusion syndrome, first trimester
O43.021 is a valid, billable ICD-10-CM code for fetus-to-fetus placental transfusion syndrome, first trimester. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.Short description: Fetus-to-fetus placental transfuse syndrome, first trimester
Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data
About O43.021
O43.021 is the ICD-10-CM diagnosis code for Fetus-to-fetus placental transfusion syndrome, first trimester. It belongs to category O43 (placental disorders), block O30-O48 (maternal care related to the fetus and amniotic cavity and possible delivery problems) and chapter 15 (pregnancy, childbirth and the puerperium). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.
Within O43.02 (Fetus-to-fetus placental transfusion syndrome), O43.021 is specifically for Fetus-to-fetus placental transfusion syndrome, first trimester. Related codes cover second trimester (O43.022), third trimester (O43.023) and unspecified trimester (O43.029).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 817 (Other Antepartum Diagnoses with O.R. Procedures with MCC, relative weight 2.0534), DRG 818 (Other Antepartum Diagnoses with O.R. Procedures with CC, relative weight 1.2942), DRG 819 (Other Antepartum Diagnoses with O.R. Procedures without CC/MCC, relative weight 0.7739), DRG 831 (Other Antepartum Diagnoses without O.R. Procedures with MCC, relative weight 1.1558), DRG 832 (Other Antepartum Diagnoses without O.R. Procedures with CC, relative weight 0.7585) and DRG 833 (Other Antepartum Diagnoses without O.R. Procedures without CC/MCC, relative weight 0.5002), in MDC 14 (Pregnancy, Childbirth and the Puerperium), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
The Medicare Code Editor treats this as a maternity diagnosis, expected only for patients age 9 through 64.
It is on the CMS list of diagnoses consistent only with female patients (the sex-conflict edit itself was retired in FY2025).
It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.
Before ICD-10, this condition was coded in ICD-9-CM as 656.71 (other placental conditions, affecting management of mother, delivered, with or without mention of antepartum condition) and 656.73 (other placental conditions, affecting management of mother, antepartum condition or complication).
Notes that apply from higher levels
Instructions written at a parent level also apply to O43.021.
› From O43 Placental disorders
Broader instructions also apply from Chapter 15: Pregnancy, childbirth and the puerperium.
MS-DRG v44.0 grouping
All DRGs →Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.
MDC 14 · Pregnancy, Childbirth and the Puerperium
ICD-9-CM equivalent
Converter →- 656.71Other placental conditions, affecting management of mother, delivered, with or without mention of antepartum conditionapproximate
- 656.73Other placental conditions, affecting management of mother, antepartum condition or complicationapproximate
From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.
Code history
- 2016
- 2017
- 2018
- 2019
- 2020
- 2021
- 2022
- 2023
- 2024
- 2025
- 2026
- 2027
- FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
- No changes since FY2016.
Common questions about O43.021
Is O43.021 billable?
- Yes. O43.021 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can O43.021 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict O43.021 as a principal diagnosis.
Is O43.021 a CC or MCC?
- No. O43.021 is neither a CC nor an MCC under MS-DRG v44.0.
What DRG does O43.021 group to?
- O43.021 is used in the MS-DRG v44.0 logic for MS-DRG 817 (Other Antepartum Diagnoses with O.R. Procedures with MCC), MS-DRG 818 (Other Antepartum Diagnoses with O.R. Procedures with CC), MS-DRG 819 (Other Antepartum Diagnoses with O.R. Procedures without CC/MCC), MS-DRG 831 (Other Antepartum Diagnoses without O.R. Procedures with MCC), MS-DRG 832 (Other Antepartum Diagnoses without O.R. Procedures with CC) and MS-DRG 833 (Other Antepartum Diagnoses without O.R. Procedures without CC/MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.
What is the ICD-9 code for O43.021?
- The CMS General Equivalence Mappings map O43.021 to ICD-9-CM 656.71 and 656.73.