O66.40 Failed trial of labor, unspecified

The ICD-10-CM code for Failed trial of labor, unspecified is O66.40 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Chapter

15: Pregnancy, childbirth and the puerperium (O00-O9A)

Section

O60-O77: Complications of labor and delivery (O60-O77)

Category O66

12 codes (10 billable)

FY2026 Status

Stable since FY2024

Also Known As

ICD-10-CM Alphabetic Index entries that lead to O66.40:

• Failure, failed › trial of labor (with subsequent cesarean delivery)
• Delivery (childbirth) (labor) › cesarean (for) › failed › trial of labor NOS
• Delivery (childbirth) (labor) › complicated › by › failed › trial of labor

U.S. Hospital Utilization

• An estimated 2,455 U.S. inpatient stays in 2023 included O66.40 among the documented diagnoses.
• 335 stays listed it as the principal diagnosis.

Source: National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality, 2016–2023. National survey-weighted estimates.

References

• CMS — ICD-10-CM Official Code Set and Guidelines, FY2026
• CDC/NCHS — ICD-10-CM Files and Browser Tool
• AHRQ — HCUP National Inpatient Sample, Frequencies by Diagnosis Code (2016–2023)