Z3A
Non-Billable (Header)Weeks of gestation
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
What This Code Means
Z3A is the ICD-10-CM diagnosis code for weeks of gestation. Z3A sits in the ICD-10-CM chapter for factors influencing health status and contact with health services (z00-z99), within the section covering persons encountering health services in circumstances related to reproduction (z30-z39).
Header codes like Z3A 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 Z3A'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.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for Z3A sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.