Hoping for a VBAC?

In a call with my High Risk Pregnancy Clients last week, we covered - What the heck is a VBAC Calculator?

VBAC calculators are online tools used by physicians to estimate the likelihood of a successful vaginal birth after a previous cesarean section. These calculators typically consider a handful of things, including:

• Maternal age

• Body Mass Index (BMI)

• History of prior vaginal births

• Indication for the previous C-section

• Gestational age

• Presence of labor at the time of evaluation

Benefits of VBAC Calculators

1. Evidence-Based Decision Making: VBAC calculators use data from large studies to provide a statistical likelihood of success, which can help inform discussions between healthcare providers and patients.

2. Risk Assessment: They can help identify patients who might have a higher or lower chance of successful VBAC, aiding in personalized care planning.

3. Efficiency: These tools can facilitate faster and more systematic evaluations during prenatal visits, potentially saving time for both physicians and patients.

Concerns and Limitations

1. Over-reliance on Scores: Critics argue that using VBAC prediction scores as the primary basis for clinical decisions can lead to an over-reliance on statistical models, which might not fully capture the nuances of individual patient situations.

2. Inflexibility: Some argue that these scores can create a sense of inflexibility, discouraging trials of labor in cases where a woman might prefer to attempt a VBAC despite a lower predicted success rate.

3. Risk of Bias: The data and algorithms behind these calculators are based on population-level statistics, which may not apply equally to all individuals, potentially leading to biased recommendations.

4. Patient Autonomy: There is concern that the use of VBAC calculators might undermine patient autonomy by prioritizing statistical predictions over the personal preferences and values of the pregnant person.

Balancing Clinical Guidance with Patient Preferences

1. Informed Consent: It's crucial that patients receive comprehensive information about the risks and benefits of both VBAC and repeat C-sections. This includes discussing the limitations of VBAC calculators and how they fit into the broader context of care.

2. Shared Decision-Making: Physicians and patients should engage in shared decision-making, where the patient's values, preferences, and experiences are given significant weight alongside clinical guidelines and statistical predictions.

3. Respecting Choices: Healthcare providers should respect and support a woman's informed choice regarding VBAC, even if the prediction score suggests a lower likelihood of success, as long as it is medically reasonable to do so.

4. Continuous Monitoring and Support: If a trial of labor is pursued, continuous monitoring and support should be provided to ensure the safety and well-being of both the mother and baby.

Ethical Considerations

1. Non-Maleficence: Healthcare providers must ensure that the use of VBAC calculators does not harm patients by leading to unnecessary C-sections or discouraging trials of labor that might otherwise be safe.

2. Beneficence: The primary goal should always be to promote the best possible outcomes for both the mother and baby, which involves considering both medical evidence and patient preferences.

3. Justice: Access to VBAC should be equitable, and decisions should not be influenced by biases related to age, BMI, race, or other non-medical factors.

VBAC calculators can be valuable tools for guiding clinical decisions, but they should not overshadow the importance of your preferences and values. A BALANCED approach that integrates evidence-based risk assessment with personalized care and shared decision-making is essential for empowering you and ensuring the best possible outcomes.

Here are a few articles I found against the use of VBAC calculators:

AMA Ethics - Why Equitable Access to Vaginal Birth Requires Abolition of Race-Based Medicine

AMA Ethics - How Should Clinicians Respond to Race-Based Algorithms as Sources of Iatrogenic Harm?

VBAC Facts® - New study reveals surprising truths about the VBAC calculator​

Here are 4 concerns I have with these calculators:

Bias and Inequity: Critics argue that VBAC calculators often incorporate race and ethnicity as factors, which can perpetuate racial biases and inequities in healthcare. For instance, race-based adjustments in these calculators have been shown to lower the predicted success rates of VBAC for African American and Hispanic women, not due to inherent medical reasons but because of historical and contemporary inequities. This can lead to reduced autonomy for these women in making informed decisions about their childbirth options, as their preferences might be overshadowed by biased risk assessments​

Limitations in Accuracy: Some studies have found that VBAC calculators, such as the Grobman calculator, can be inaccurate, especially at lower predicted success rates. These calculators tend to under-predict actual VBAC success when the predicted probability is less than 60%. This inaccuracy can discourage women with lower predicted success rates from attempting a VBAC, potentially leading to unnecessary repeat cesarean sections​.

Impact of Provider and Institutional Bias: The accuracy and utility of VBAC calculators are also influenced by provider and institutional preferences. For instance, provider reluctance to support VBAC in patients with higher BMIs or those from certain racial backgrounds can skew the data used in these calculators, further compounding biases. This can result in a self-fulfilling prophecy where patients deemed to have lower VBAC odds are not given adequate support to attempt a VBAC, thereby lowering the overall success rates reported for these groups​.

Patient Autonomy and Informed Consent: There is a growing call for healthcare providers to prioritize patient autonomy and informed consent over the use of predictive algorithms. Bioethicists recommend that women's preferences and values should take precedence in VBAC decision-making, and that clinicians should engage in more nuanced discussions with patients about the limitations and potential biases of these tools​​.

An OB told one of my clients, “If you want to get two OBs fighting, bring up VBAC Calculators!”