The VBAC Calculator: What It Is, Why It’s Used, and Why It Shouldn’t Be Making Decisions About Your Birth

The Statesville Doula
1 day ago
4 min read

A laboring mom leaning over the hospital bed breathing through contractions

If you’re planning a VBAC (Vaginal Birth After Cesarean), there’s a good chance your provider has mentioned something called a VBAC calculator. For many parents, this tool is introduced early in pregnancy and presented as an objective way to determine whether a VBAC is a “good option.”

But the truth is, the VBAC calculator is deeply flawed, biased, and often misused in ways that limit informed consent and bodily autonomy. As a doula in Charlotte, N.C., I’ve seen how much power this single number is given... and how much harm it can quietly cause. I see how this calculator can limit options, undermine confidence, and quietly steer families toward repeat cesareans... sometimes without full, informed consent.

Let’s discuss this a bit.

What Is the VBAC Calculator?

The VBAC calculator is a statistical tool designed to estimate the likelihood that someone will have a successful vaginal birth after a prior cesarean. It uses population-based data and factors such as:

Age
Height and weight (BMI)
Prior vaginal birth
Reason for prior cesarean
Gestational age
Whether labor is spontaneous or induced

Earlier versions of the calculator also included race and ethnicity as predictors.

The result is given as a percentage—often framed as your “chance” of a successful VBAC.

Why Providers Use the VBAC Calculator

In theory, the VBAC calculator was created to help clinicians counsel patients and assess risk. In practice, it’s often used to:

Decide who is “allowed” to attempt a VBAC
Justify hospital or provider VBAC cutoffs
Recommend repeat cesareans early in pregnancy
Discourage VBACs under the guise of “safety”

The calculator gives the illusion of objectivity. A number feels scientific. Definitive. Hard to argue with. Because it produces a numerical score, the calculator is often perceived as objective or evidence-based. But numbers can be misleading—especially when the tool itself is biased.

But that’s exactly the problem.

How the VBAC Calculator Is Biased

1. It Uses Population Data, Not Individual Context

The VBAC calculator is based on averages across large groups of people. It does not account for:

Quality of labor support
Use of a doula
Provider experience with VBAC
Hospital culture and policies
Trauma or circumstances surrounding the prior cesarean
Patient values, preferences, or goals

Your labor is not an average, and your body is not a data point.

Repeat this to yourself:

"My body is not a statistic."

2. Race-Based Medicine Was Built Into It

Earlier versions of the VBAC calculator lowered success rates for people identified as Black or Hispanic. Let that sink in.

Race is not a biological risk factor. Including it in the equation reinforced systemic racism, not medical accuracy. Even though race has since been removed from newer versions, the damage and mindset remain... and many providers were trained using the older, biased model.

3. BMI Is Overweighted (NO pun intended)

Higher BMI significantly lowers the predicted success rate, despite evidence that BMI alone is a poor predictor of labor outcomes. This disproportionately affects plus-size birthers and reinforces weight bias in obstetric care (which we do not need more of) without reflecting real-world outcomes or individualized care.

4. It Assumes the Prior Cesarean Was Necessary

The calculator often penalizes people whose prior cesarean was for “failure to progress” or “arrest of labor”... without examining why labor stalled. More on the term "Failure to Progress" in a later blog post that I'll attach soon.

Was labor induced early?
Was movement restricted?
Were time limits imposed?
Was continuous labor support available?

These critical factors are ignored, even though they significantly impact outcomes.

5. It Ignores the Provider’s Role

VBAC success is heavily influenced by:

Provider patience
Their willingness to allow time
Their comfort managing VBAC labors
Their avoidance of unnecessary interventions

The calculator does not measure provider skill or bias—yet it’s often used to justify those very limitations.

Why the VBAC Calculator Should Not Decide Your Birth Options

A Percentage Is Not a Prediction

A VBAC calculator score does not predict what will happen in your labor. It reflects what happened to a group of people under specific circumstances—many of which may not apply to you.

It cannot measure:

Your body’s ability to labor
The quality of your support
Your informed decision-making
Your provider’s approach

It Undermines Informed Consent

Too often, the VBAC calculator is used to shut down discussion rather than open it. When a number is presented as a reason to deny or discourage VBAC, true informed consent is lost.

Informed consent requires:

Balanced discussion of VBAC and repeat cesarean risks
Respect for patient autonomy
Shared decision-making

A calculator should never replace these conversations.

It Can Erode Confidence Before Labor Begins

Many families walk away from early prenatal visits feeling discouraged or afraid because a calculator told them they were “unlikely” to succeed.

Confidence, safety, and support matter in labor. No tool should take those away before labor even begins.

What Should Be Used Instead?

Rather than relying on a VBAC calculator, families deserve:

Individualized counseling
Evidence-based discussions of risks and benefits
A thorough review of prior birth with context
Honest conversations about hospital policies
Supportive providers and continuous labor support

VBAC is not just about statistics — it’s about autonomy, respect, and evidence-based care.

Final Thoughts

The VBAC calculator is not neutral.

It is not personalized.

It should never determine your options.

You are more than a percentage.

Your birth is not a formula.

You deserve care that honors your body, your history, and your right to make informed choices. If you need support, more information, or doula support to help you achieve your VBAC, PLEASE reach out. As Charlotte and Lake Norman area, NC's Certified VBAC doula, I would LOVE to talk to you, no obligation of course.

Schedule a Discovery Call

Peace, love, and babies,

Staci