O16.4Unspecified maternal hypertension, complicating childbirth

O16.4 is the ICD-10-CM diagnosis code for unspecified maternal hypertension, complicating childbirth. It belongs to category O16 (unspecified maternal hypertension), block O10-O16 (edema, proteinuria and hypertensive disorders in pregnancy, childbirth and the puerperium) 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 O16 (unspecified maternal hypertension), O16.4 is specifically for unspecified maternal hypertension, complicating childbirth. Related codes cover first trimester (O16.1), second trimester (O16.2), third trimester (O16.3), complicating the puerperium (O16.5) and unspecified trimester (O16.9).

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 998 (Principal Diagnosis Invalid as Discharge Diagnosis), 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 was added in FY2017, effective October 1, 2016.

Before ICD-10, this condition was coded in ICD-9-CM as 642.91 (unspecified hypertension complicating pregnancy, childbirth, or the puerperium, delivered, with or without mention of antepartum condition).