This page compares two distinct NUCC-taxonomy specialties tracked by the CMS National Plan and Provider Enumeration System: Inpatient Obstetric Registered Nurse, which currently counts 578 enrolled providers across 52 U.S. states and territories, and Registered Nurse, with 177,204 providers across 56 states. Each clinician on these rosters selected a primary NUCC code at NPI enrollment, so the totals measure how many providers self-identify their primary practice as Inpatient Obstetric Registered Nurse or Registered Nurse rather than the total population ever trained or credentialed in either field — dual-certified clinicians show up under whichever code they registered first.

On national volume, Registered Nurse carries the larger provider roster (177,204 vs 578), and Registered Nurse has the wider geographic footprint at 56 states versus 52. The top Inpatient Obstetric Registered Nurse concentration sits in California (55 providers), while Registered Nurse peaks in New York (27,515). The per-capita columns in the table below normalize each state's raw count against 2023 Census population estimates, which matters because absolute provider counts track population scale first and specialty density second — a small state with a strong training pipeline can out-rank a larger state on per-100K availability.

Use this comparison to understand relative availability, not to judge clinical substitutability — Inpatient Obstetric Registered Nurse and Registered Nurse are distinct specialties with different scopes of practice, training requirements, and conditions they treat, even when their NUCC categories overlap. Important: PlainDoctor is a directory of publicly available CMS government data, not medical advice, a provider rating, or a recommendation about which specialty a patient should consult. Always work with a licensed clinician to determine which specialty is appropriate for your condition, verify any specific provider through the NPPES NPI Registry and the relevant state medical board, and consult the NUCC taxonomy documentation for the formal scope-of-practice definitions behind each specialty code.