{"uid":"cap_iqT-sDTijId4AzF24Ap1p","slug":"grobman-2007-vbac-probability-calculator-first-prenatal-visit-47b3f3e2","name":"Grobman 2007 VBAC Probability Calculator (First Prenatal Visit)","description":"Grobman 2007 first prenatal visit logistic probability of vaginal birth after cesarean from maternal age, prepregnancy BMI, caller-assigned ethnicity (african_american, hispanic, or other), any prior vaginal delivery, prior VBAC after cesarean, and recurrent cesarean indication. Ethnicity uses the paper terms; magent does not assign race or ethnicity. Not the 2009/2010 admission model and not Grobman 2021. Not a trial-of-labor order.","url":"https://api.magentlab.com/api/calc/grobman_vbac","method":"GET","headers":{},"bodySchema":{"type":"object","$schema":"https://json-schema.org/draft/2020-12/schema","required":["input"],"properties":{"input":{"type":"object","required":["type","method"],"properties":{"type":{"type":"string","const":"http"},"method":{"enum":["GET","HEAD","DELETE"],"type":"string"},"headers":{"type":"object","additionalProperties":{"type":"string"}},"queryParams":{"type":"object","required":["age","bmi_kg_m2","ethnicity","prior_vaginal","prior_vbac","recurrent_indication"],"properties":{"age":{"type":"integer","description":"Maternal age in years (integer 12-55). Grobman 2007 coefficient -0.039 per year. 12-55 is a clinical range for TOLAC; the paper does not print that clamp. magent does not take a date of birth."},"bmi_kg_m2":{"type":"number","description":"Prepregnancy BMI in kg/m^2 (15-70). Grobman 2007 coefficient -0.060. 15-70 is a clinical range; the paper does not print that clamp. Caller-supplied; magent does not compute BMI from height and weight."},"ethnicity":{"enum":["african_american","hispanic","other"],"type":"string","description":"Caller-assigned ethnicity as used in Grobman 2007: african_american, hispanic, or other (mutually exclusive paper terms; other is the reference). magent does not assign race or ethnicity."},"prior_vbac":{"type":"boolean","description":"VBAC after prior cesarean as assigned by the caller (Grobman 2007). true scores +1.003. true or false. magent does not infer this from prior_vaginal."},"prior_vaginal":{"type":"boolean","description":"Any prior vaginal delivery as assigned by the caller (Grobman 2007). true scores +0.888. true or false. magent does not read the obstetric history."},"recurrent_indication":{"type":"boolean","description":"Recurring indication for cesarean as assigned by the caller (Grobman 2007). true scores -0.632. true or false. magent does not read the operative indication."}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object"}}}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.005","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.005/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_imBbM9v6VEz0Ov4IOOkss","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.005","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Computes the Grobman 2007 logistic regression probability of vaginal birth after cesarean (VBAC) at the first prenatal visit using maternal age, prepregnancy BMI, ethnicity, and obstetric history flags","exampleAgentPrompt":"What's the Grobman 2007 first-prenatal-visit VBAC probability for a 34-year-old patient with a prepregnancy BMI of 28.5, ethnicity 'other', who has had a prior vaginal delivery, a prior VBAC, and whose prior cesarean was not for a recurrent indication?","exampleUseCases":[{"title":"Prenatal VBAC counseling probability estimate","prompt":"I need the Grobman 2007 VBAC probability for a patient who is 29 years old, prepregnancy BMI 31, Hispanic, no prior vaginal deliveries, no prior VBAC, and the original cesarean indication is not recurrent — what's her predicted chance of successful VBAC?"},{"title":"High-BMI older patient VBAC risk stratification","prompt":"Can you calculate the first-prenatal-visit Grobman 2007 VBAC score for a 42-year-old patient with a prepregnancy BMI of 38, ethnicity 'other', no prior vaginal delivery, no prior VBAC, and a recurrent cesarean indication?"},{"title":"Favorable-history VBAC probability for African American patient","prompt":"Run the Grobman 2007 prenatal VBAC probability for a 27-year-old African American patient with a prepregnancy BMI of 24, a prior vaginal delivery, a prior VBAC, and no recurrent cesarean indication."}],"resultDescription":"Returns a numeric probability (0–1 logistic score) representing the predicted likelihood of achieving a vaginal birth after cesarean at the time of the first prenatal visit, derived from the Grobman 2007 regression coefficients applied to the supplied maternal age, prepregnancy BMI, ethnicity category, and three obstetric history boolean flags.","failureModes":["Missing required query parameter (age, bmi_kg_m2, ethnicity, prior_vaginal, prior_vbac, or recurrent_indication) returns a 400/422 validation error","Age outside clinical range 12–55 or BMI outside 15–70 may be rejected or flagged","Invalid ethnicity value not in [african_american, hispanic, other] returns a validation error","Payment not included or insufficient (x402 protocol) returns 402 Payment Required","Non-integer age value returns a schema validation error"],"whenToPreferThis":"Use this endpoint when you need the Grobman 2007 first-prenatal-visit VBAC probability specifically — not the 2009/2010 admission-time model and not the 2021 update. It is appropriate for prenatal counseling contexts where age, prepregnancy BMI, and obstetric history are known at the first visit. Prefer this over generic calculators when the clinical protocol explicitly references Grobman 2007 or when comparing against published first-prenatal-visit nomograms.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-14T06:41:09.361Z","isFirstParty":false}