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DATA · MAY 8, 2026

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© 2026 FONTEUM RESEARCH · DATA SNAPSHOT MAY 8, 2026 · BUILT WITH CARE

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Methodology/Obstetrics & Gynecology Provider Supply by State
METHODOLOGY · v2026.05.0

Obstetrics & Gynecology Provider Supply by State

Active U.S. OB-GYN physicians per 100,000 residents, by state.

Version v2026.05.0Last refreshed May 6, 2026Cadence Quarterly NPPES refresh; annual Census denominator update.
Audit PackResearch studySources registryCorrections log

What this methodology is

This page is the public, versioned methodology for the Obstetrics & Gynecology Provider Supply by State dataset. It documents how every figure on the matched Fonteum Research study, /api/v1 endpoint, and Audit Pack was constructed — from registered public-source ingest through aggregation rules to the rendered output. It exists so buyers can satisfy auditor questions by linking to a single durable URL.

Every section below is the source of truth. Where the methodology differs from the underlying source's own description (for example: which taxonomies count, how Type-1 vs Type-2 NPIs are treated, how density per 100k is computed), the rule lives here, not in the source. Methodology versions (v2026.05.0 today) increment when those rules change; data refreshes within a methodology version are tracked separately under refresh historyand surface as the “Last refreshed” banner above.

Source provenance

Source families
CMS NPPES NPI Registry (public API) + U.S. Census Bureau Population Estimates Program (PEP) V2025
Spatial resolution
State (50 + DC). NPPES does not publish a county-level field of practice in its public API.
Temporal coverage
2026 snapshot (NPPES queried 2026-05-06; Census 2024 vintage).
Refresh cadence
Quarterly NPPES refresh; annual Census denominator update.
Snapshot scope
8,572 OB-GYNs across 51 states + DC; snapshot dated May 6, 2026.

The Fonteum sources registry holds the canonical entry for each source family — Tier classification, ToS posture, refresh schedule, and live-vs-pending status: /sources.

Reproducibility statement

An independent researcher with access only to the public sources listed above can recreate this dataset by following these steps. Discrepancies between an independent reproduction and the published figures belong in /corrections-log; we publish them when they arise.

1. Query the NPPES API at https://npiregistry.cms.hhs.gov/api/ with taxonomy_description=<NUCC name> and enumeration_type=NPI-1 for each NUCC taxonomy in the parent specialty's scope (full list in the parent study's methodology). 2. Filter results to records with active license status. 3. Bucket by practice-address state (50 USPS codes + DC). 4. Pull U.S. Census Bureau PEP V2025 (2024 vintage) state population estimates from https://www.census.gov/programs-surveys/popest.html. 5. Compute per_100k = count ÷ population × 100,000 per state. Rank ascending and bucket into quartiles by rank. 6. Apply the parent study's transparent underserved threshold to flag the per-state row's underserved boolean. The full ingest script is published at scripts/research/nppes-write.ts in the Fonteum engine repository (private). Customers under a pilot or Standard agreement can request the script for independent reconciliation.

Limitations

Limitations are surfaced explicitly, not buried. Each item below is a constraint a buyer’s compliance team should review before relying on the dataset for a specific use case.

  • Counts NPI-1 individual providers only; the parent specialty taxonomy plus any subspecialty taxonomies the §183 / §188 ingest scoped to. PAs / NPs / CNMs working in the same care setting under different taxonomy codes are out of scope.
  • Dataset measures density (per-capita supply), not access. Drive time, appointment availability, insurance acceptance, and wait times are not modeled.
  • Underserved threshold is the parent study's transparent baseline cutoff, not a regulatory or clinical definition.
  • Provider state is the practice-address state in NPPES. NPPES does not publish a county-level field of practice in its public API; county queries surface state-level density.
  • NPPES last_updated reflects when CMS last touched the record — providers may have moved, retired, or changed practice settings without updating their NPPES record. Roughly 5-15% of records have last_updated > 5 years per CMS published quality reports.
  • U.S. Census Bureau PEP V2025 (2024 vintage) state population. Annual estimates between decennial counts; Census itself documents a confidence band of ~0.5-2% depending on state.
  • Estimates do not reflect mid-2025+ population movements. Major hurricane / wildfire displacements may distort per-capita ratios for several quarters until next vintage.

Field schema

Every field surfaced from this dataset on the API and rendered surfaces. Source, refresh cadence, and confidence are recorded per field, not per dataset.

FieldDescriptionSourceRefreshConfidence
npiIndividual provider NPI (10-digit).CMS NPPES NPI Registry (public API) ↗Quarterly1.0 (verbatim)
taxonomy_codesAll NUCC taxonomy codes attached to the record (primary + subspecialties).CMS NPPES NPI Registry (public API) ↗Quarterly1.0 (verbatim)
taxonomy_primaryThe provider's primary NUCC taxonomy code.CMS NPPES NPI Registry (public API) ↗Quarterly1.0 (verbatim)
statePractice-address state (USPS code) at the time of NPPES record's last_updated.CMS NPPES NPI Registry (public API) ↗Quarterly1.0 (verbatim)
cityPractice-address city at the time of NPPES record's last_updated.CMS NPPES NPI Registry (public API) ↗Quarterly1.0 (verbatim)
last_updatedWhen CMS last modified the NPPES record. Reflects record freshness, not Fonteum snapshot date.CMS NPPES NPI Registry (public API) ↗Quarterly1.0 (verbatim)

Version history

Every methodology version bump is recorded here with the change rationale. Data-only refreshes (no methodology change) appear as same-version entries with a refresh date.

VersionReleasedWhat changed
v2026.05.0currentMay 6, 2026Initial Audit Pack release. Methodology, provenance map, reproducibility statement, and limitations stack baselined.

Cite this methodology

For procurement attachments, audit responses, footer attribution, or academic use. Pick a format and copy.

Fonteum. (2026). Obstetrics & Gynecology Provider Supply by State (v2026.05.0) [Dataset]. Directory Ventures, LLC. https://fonteum.com/methodology/obgyn-supply

Downloads & cross-references

Download methodology PDF (v2026.05.0)View Audit Pack →
  • Research study → the editorial findings + charts
  • JSON methodology metadata — for programmatic ingestion
  • Download per-state CSV
  • Download per-state JSON

Methodology questions: methodology@fonteum.com. Data corrections: /corrections-log. B2B inquiries: api@fonteum.com.

This page is the durable URL a buyer’s compliance officer can link from their product. The version pinned at the URL (v2026.05.0) is the active methodology; historical versions remain accessible at the same URL with prior-version content available in the Version history table.

population_2024PEP V2025 state population estimate for 2024 vintage.U.S. Census Bureau Population Estimates Program (PEP) V2025 ↗Annual (V<year> vintage releases each March)1.0 (verbatim)
countOB-GYNs active in NPPES as of snapshot date. The §193 sub-specialty filter parameter (`?subspecialty=<NUCC code>`) on the public API recomputes counts and density against any registered subspecialty taxonomy.Fonteum Research (derived from CMS NPPES + U.S. Census Bureau)Recomputed on each NPPES + Census refresh cycle0.95
per_100kOB-GYNs per 100,000 residents (count ÷ population × 100,000).Fonteum Research (derived from CMS NPPES + U.S. Census Bureau)Recomputed on each NPPES + Census refresh cycle0.95
rank_density1..51 rank by per_100k across U.S. states + DC.Fonteum Research (derived from CMS NPPES + U.S. Census Bureau)Recomputed on each NPPES + Census refresh cycle0.95
rank_count1..51 rank by absolute count.Fonteum Research (derived from CMS NPPES + U.S. Census Bureau)Recomputed on each NPPES + Census refresh cycle0.95
quartileQ1..Q4 from rank_density.Fonteum Research (derived from CMS NPPES + U.S. Census Bureau)Recomputed on each NPPES + Census refresh cycle0.95
underservedBoolean: per_100k below the transparent threshold defined in the parent study.Fonteum Research (derived from CMS NPPES + U.S. Census Bureau)Recomputed on each NPPES + Census refresh cycle0.90