O00.521Right cornual ectopic pregnancy with intrauterine pregnancy

O00.521 is the ICD-10-CM diagnosis code for right cornual ectopic pregnancy with intrauterine pregnancy. It belongs to category O00 (ectopic pregnancy), block O00-O08 (pregnancy with abortive outcome) 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 O00.52 (cornual ectopic pregnancy with intrauterine pregnancy), O00.521 is specifically for right cornual ectopic pregnancy with intrauterine pregnancy. Related codes cover left cornual ectopic pregnancy with intrauterine pregnancy (O00.522) and unspecified cornual ectopic pregnancy with intrauterine pregnancy (O00.529).

Use an additional code from category O08 to identify any associated complication.

As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.

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 was added in FY2027, effective October 1, 2026.