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ICD-10-CM 2027

ICD-10 code for trial of labor failure

O66.40

Failed trial of labor, unspecified

✓ Billable / specificMaternity · age 9–64Female only

From the official ICD-10-CM alphabetic index entry “Failure, failed › trial of labor (with subsequent cesarean delivery)”. Page updated September 29, 2026.

About coding trial of labor failure

The ICD-10-CM code for trial of labor failure is O66.40 (Failed trial of labor, unspecified). The official index lists 1 more specific code, so check the documentation for details such as type, cause, site or severity before settling on O66.40.

Within O66.4, choose O66.40 (unspecified) only when documentation doesn't support a more specific option: attempted vaginal birth after previous cesarean delivery (O66.41).

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.

More specific trial of labor failure codes (official index)

  • following previous cesarean delivery O66.41 — Failed attempted vaginal birth after previous cesarean delivery

Common questions about trial of labor failure ICD-10 codes

What is the ICD-10 code for trial of labor failure?

O66.40 — Failed trial of labor, unspecified. More specific codes apply when the documentation supports them: O66.41.

Is O66.40 billable?

Yes. O66.40 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can O66.40 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict O66.40 as a principal diagnosis.

Is O66.40 a CC or MCC?

No. O66.40 is neither a CC nor an MCC under MS-DRG v44.0.