O16 ICD-10-CM Code: Unspecified maternal hypertension

O16 is the ICD-10-CM diagnosis code for unspecified maternal hypertension. O16 sits in the ICD-10-CM chapter for pregnancy, childbirth and the puerperium (o00-o9a), within the section covering edema, proteinuria and hypertensive disorders in pregnancy, childbirth and the puerperium (o10-o16).

Header codes like O16 cannot be reported on claims directly, they organize child codes that share clinical context but the actual diagnosis must be coded to the highest level of specificity supported by the documentation. Coders should look at O16's child codes and select the one that matches the patient's documented presentation, since payers reject header codes submitted as the primary diagnosis. For risk adjustment workflows, header codes never contribute to a Medicare Advantage member's RAF score on their own; only billable child codes that happen to map to a payment HCC affect risk-adjusted plan payments.