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Grobman 2007 first-visit VBAC

Grobman VBAC

Compute the Grobman 2007 first-prenatal-visit logistic probability of vaginal birth after cesarean from maternal age, prepregnancy BMI, caller-assigned ethnicity, any prior vaginal delivery, prior VBAC after cesarean, and recurrent cesarean indication.

LIVE $0.005 USDC GET /api/calc/grobman_vbac

Markdown: /docs/grobman-vbac.md · Canonical: https://magentlab.com/docs/grobman-vbac

Not a medical device. Not a diagnosis, dose, or listing recommendation.

What it computes

Compute the Grobman 2007 first-prenatal-visit logistic probability of vaginal birth after cesarean from maternal age, prepregnancy BMI, caller-assigned ethnicity, any prior vaginal delivery, prior VBAC after cesarean, and recurrent cesarean indication.

When to use

When an agent already has Grobman 2007 first-visit predictors and needs that paper's probability. Not a trial-of-labor order, not the Flamm admission score, not the 2009/2010 admission model, and not Grobman 2021.

When not to use

• Not a medical device and not a trial-of-labor or cesarean order.
• ethnicity is caller-assigned as african_american, hispanic, or other using Grobman 2007 terms. magent does not assign race or ethnicity.
• Grobman 2007 first prenatal visit logistic model only. Not the 2009/2010 admission or intrapartum model. A later MFMU model without race/ethnicity exists (Grobman 2021) and is not this tool.
• Age 12-55 and BMI 15-70 are clinical ranges for TOLAC. Grobman 2007 does not print those clamps.
• prior_vaginal, prior_vbac, and recurrent_indication are caller-assigned independently. magent does not infer obstetric history.

Formula

w = 3.766 - 0.039*age_years - 0.060*prepregnancy_bmi - 0.671*[african_american] - 0.680*[hispanic] + 0.888*[any prior vaginal delivery] + 1.003*[VBAC after prior cesarean] - 0.632*[recurring indication for cesarean]; vbac_probability = exp(w)/(1+exp(w)); ethnicity african_american|hispanic|other (caller-assigned Grobman 2007 terms, mutually exclusive; other is the reference; magent does not assign race or ethnicity); flags 1 if true else 0; first prenatal visit model; round linear_predictor and vbac_probability 3 decimals; not Grobman 2009/2010 admission; not Grobman 2021 race-free; not a TOLAC order

Citation

Title

Development of a nomogram for prediction of vaginal birth after cesarean delivery

Authors

Grobman WA, Lai Y, Landon MB, Spong CY, Leveno KJ, Rouse DJ, Varner MW, Moawad AH, Caritis SN, Harper M, Wapner RJ, Sorokin Y, Miodovnik M, Carpenter M, Peaceman AM, O'Sullivan MJ, Sibai BM, Langer O, Thorp JM, Ramin SM, Mercer BM; National Institute of Child Health and Human Development (NICHD) Maternal-Fetal Medicine Units Network (MFMU)

Source

Obstet Gynecol. 2007;109(4):806-812

DOI

10.1097/01.AOG.0000259312.36053.02

Worked example

Also searched as

• Grobman VBAC
• Grobman 2007 nomogram
• first prenatal visit VBAC
• MFMU VBAC prediction
• vaginal birth after cesarean probability
• TOLAC success probability
• Grobman first visit model
• NICHD MFMU VBAC

Try

Opens the live endpoint. Unpaid browser requests show the paywall; agents should send Accept: application/json.

/api/calc/grobman_vbac?age=30&bmi_kg_m2=25&ethnicity=other&prior_vaginal=false&prior_vbac=false&recurrent_indication=false

Full URL: https://api.magentlab.com/api/calc/grobman_vbac?age=30&bmi_kg_m2=25&ethnicity=other&prior_vaginal=false&prior_vbac=false&recurrent_indication=false

Call

Expect HTTP 402 until you retry with PAYMENT-SIGNATURE. Incomplete query params return HTTP 400 before any quote or charge.

curl -i -H "Accept: application/json" "https://api.magentlab.com/api/calc/grobman_vbac?age=30&bmi_kg_m2=25&ethnicity=other&prior_vaginal=false&prior_vbac=false&recurrent_indication=false"

Parameters

Bulk (POST)

POST the same path with a JSON items array. The first item is the GET unit; each additional item is $0.002. Invalid items return HTTP 400 before settlement.

POST /api/calc/grobman_vbac Max 25 unit_amount + extra_item_amount * (n - 1) extra $0.002 PREVIEW

• 1 to 25 items. Each item uses the same keys as the GET query parameters.
• POST of 1 item costs the same as GET. Lists longer than 25: chunk into multiple POSTs. Extra items still execute; do not pad dummy rows.
• The first invalid item fails the whole request (index in the 400 JSON). You are not charged.
• HTTP 200 is {count, path, items}. Each items[i] is the GET 200 body for that row.
• Catalog misses (empty matches, found=false) stay paid 200s inside that slot.
• x402 resource URL is this path plus n and body_sha256. Browsers that prefer text/html get the same paywall as GET; Pay retries POST with the same items.

Example request (fixture)

{
  "items": [
    {
      "age": "30",
      "bmi_kg_m2": "25",
      "ethnicity": "other",
      "prior_vaginal": "false",
      "prior_vbac": "false",
      "recurrent_indication": "false"
    },
    {
      "age": "30",
      "bmi_kg_m2": "25",
      "ethnicity": "other",
      "prior_vaginal": "false",
      "prior_vbac": "false",
      "recurrent_indication": "false"
    }
  ]
}

Open bulk paywall →

Opens a two-item fixture on the API host. Unpaid browsers get the same MetaMask paywall as GET; Pay retries POST with those items.

Example 200 (fixture)

{
  "count": 2,
  "path": "/api/calc/grobman_vbac",
  "items": [
    {
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Grobman WA, Lai Y, Landon MB, Spong CY, Leveno KJ, Rouse DJ, Varner MW, Moawad AH, Caritis SN, Harper M, Wapner RJ, Sorokin Y, Miodovnik M, Carpenter M, Peaceman AM, O'Sullivan MJ, Sibai BM, Langer O, Thorp JM, Ramin SM, Mercer BM; National Institute of Child Health and Human Development (NICHD) Maternal-Fetal Medicine Units Network (MFMU)",
        "doi": "10.1097/01.AOG.0000259312.36053.02",
        "id": "grobman-2007-vbac",
        "pmid": "17400840",
        "source": "Obstet Gynecol. 2007;109(4):806-812",
        "title": "Development of a nomogram for prediction of vaginal birth after cesarean delivery"
      },
      "formula": "grobman_vbac",
      "formula_expression": "w = 3.766 - 0.039*age_years - 0.060*prepregnancy_bmi - 0.671*[african_american] - 0.680*[hispanic] + 0.888*[any prior vaginal delivery] + 1.003*[VBAC after prior cesarean] - 0.632*[recurring indication for cesarean]; vbac_probability = exp(w)/(1+exp(w)); ethnicity african_american|hispanic|other (caller-assigned Grobman 2007 terms, mutually exclusive; other is the reference; magent does not assign race or ethnicity); flags 1 if true else 0; first prenatal visit model; round linear_predictor and vbac_probability 3 decimals; not Grobman 2009/2010 admission; not Grobman 2021 race-free; not a TOLAC order",
      "age_years": 30,
      "bmi_kg_m2": 25.0,
      "linear_predictor": 1.096,
      "ethnicity": "other",
      "prior_vaginal": false,
      "prior_vbac": false,
      "recurrent_indication": false,
      "vbac_probability": 0.75
    },
    {
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Grobman WA, Lai Y, Landon MB, Spong CY, Leveno KJ, Rouse DJ, Varner MW, Moawad AH, Caritis SN, Harper M, Wapner RJ, Sorokin Y, Miodovnik M, Carpenter M, Peaceman AM, O'Sullivan MJ, Sibai BM, Langer O, Thorp JM, Ramin SM, Mercer BM; National Institute of Child Health and Human Development (NICHD) Maternal-Fetal Medicine Units Network (MFMU)",
        "doi": "10.1097/01.AOG.0000259312.36053.02",
        "id": "grobman-2007-vbac",
        "pmid": "17400840",
        "source": "Obstet Gynecol. 2007;109(4):806-812",
        "title": "Development of a nomogram for prediction of vaginal birth after cesarean delivery"
      },
      "formula": "grobman_vbac",
      "formula_expression": "w = 3.766 - 0.039*age_years - 0.060*prepregnancy_bmi - 0.671*[african_american] - 0.680*[hispanic] + 0.888*[any prior vaginal delivery] + 1.003*[VBAC after prior cesarean] - 0.632*[recurring indication for cesarean]; vbac_probability = exp(w)/(1+exp(w)); ethnicity african_american|hispanic|other (caller-assigned Grobman 2007 terms, mutually exclusive; other is the reference; magent does not assign race or ethnicity); flags 1 if true else 0; first prenatal visit model; round linear_predictor and vbac_probability 3 decimals; not Grobman 2009/2010 admission; not Grobman 2021 race-free; not a TOLAC order",
      "age_years": 30,
      "bmi_kg_m2": 25.0,
      "linear_predictor": 1.096,
      "ethnicity": "other",
      "prior_vaginal": false,
      "prior_vbac": false,
      "recurrent_indication": false,
      "vbac_probability": 0.75
    }
  ]
}

Response

Example JSON

Machine form of the same example. Frozen fixture. Not a live lookup.

{
  "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
  "citation": {
    "authors": "Grobman WA, Lai Y, Landon MB, Spong CY, Leveno KJ, Rouse DJ, Varner MW, Moawad AH, Caritis SN, Harper M, Wapner RJ, Sorokin Y, Miodovnik M, Carpenter M, Peaceman AM, O'Sullivan MJ, Sibai BM, Langer O, Thorp JM, Ramin SM, Mercer BM; National Institute of Child Health and Human Development (NICHD) Maternal-Fetal Medicine Units Network (MFMU)",
    "doi": "10.1097/01.AOG.0000259312.36053.02",
    "id": "grobman-2007-vbac",
    "pmid": "17400840",
    "source": "Obstet Gynecol. 2007;109(4):806-812",
    "title": "Development of a nomogram for prediction of vaginal birth after cesarean delivery"
  },
  "formula": "grobman_vbac",
  "formula_expression": "w = 3.766 - 0.039*age_years - 0.060*prepregnancy_bmi - 0.671*[african_american] - 0.680*[hispanic] + 0.888*[any prior vaginal delivery] + 1.003*[VBAC after prior cesarean] - 0.632*[recurring indication for cesarean]; vbac_probability = exp(w)/(1+exp(w)); ethnicity african_american|hispanic|other (caller-assigned Grobman 2007 terms, mutually exclusive; other is the reference; magent does not assign race or ethnicity); flags 1 if true else 0; first prenatal visit model; round linear_predictor and vbac_probability 3 decimals; not Grobman 2009/2010 admission; not Grobman 2021 race-free; not a TOLAC order",
  "age_years": 30,
  "bmi_kg_m2": 25.0,
  "linear_predictor": 1.096,
  "ethnicity": "other",
  "prior_vaginal": false,
  "prior_vbac": false,
  "recurrent_indication": false,
  "vbac_probability": 0.75
}

Client errors (HTTP 400)

Invalid params return 400 without charge. Shared HTTP 402 and 503 meanings: Payments.

Related tools

• Flamm VBAC score — Sum the Flamm 1997 admission VBAC points (max 10) from caller-assigned age, vaginal-birth history, first-cesarean indication, and admission cervical factors, and return the published 49% or 95% success rates only for scores 0–2 and 8–10.
• simplified Bishop score — Return the Laughon 2011 simplified Bishop score as the sum of three caller-assigned Bishop 1964 integers (dilation, station, effacement; each 0-3; max 9) and whether the score is >5.
• Bishop score — Return the Bishop 1964 pelvic score as the sum of five caller-assigned integer components (dilation, effacement, station, consistency, position).

Payment

Unpaid requests return HTTP 402 even if query parameters or POST items are missing or invalid, so CDP and agents can index the path. After a PAYMENT-SIGNATURE, invalid params return HTTP 400 JSON before settlement. magent does not charge. Fix the params, then request a new 402 quote for that complete URL. Catalog misses (empty matches, found=false) are valid paid 200s. Unpaid valid requests return HTTP 402 with a base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote: retry the same PAYMENT-SIGNATURE. Full handshake and shared payment errors: Payments. Stdio MCP: /docs/mcp.

Guarantees

• HTTP 402 is unpaid, including a missing query. After PAYMENT-SIGNATURE, invalid parameters return HTTP 400 before settlement. You are not charged. HTTP 402 never includes the tool JSON.
• exact: settlement finishes before the tool (paymentFlow upfront). batch-settlement: verify/deposit before the tool; chargedCumulativeAmount commits after HTTP 2xx. Uncertain or failed settlement fails closed (HTTP 503). Retry the same PAYMENT-SIGNATURE.
• HTTP 402 is unpaid only. Do not sign a second authorization because of a 503.
• Execution is timeout-bounded and concurrency-capped.
• Calculator inputs are stored encrypted for allowlisted operators (Magent Console). They are not in public logs, SSH lookups, catalog, or rollups. Request logs store path without query.