Birthing a child is one of the most memorable moments of one’s life. And the way a birth occurs — vaginally, or surgically by cesarean section — can influence your health and your next birth experience, if you have one. A frequently used calculator helps doctors predict the likelihood of having a successful vaginal birth after a cesarean delivery. Yet until recently, this tool may have contributed to existing health disparities, particularly between Blacks and whites. Can a newer version of this calculator help change this? And what can you do to maximize your chances of a vaginal birth after cesarean (VBAC), if that’s important to you?
Why are cesarean births sometimes necessary?
A cesarean birth is a useful and necessary procedure in certain instances, including
- when labor fails to progress
- when there is concern for the baby (such as growth restriction or heart rate issues during labor)
- issues with the placenta
- a very large baby
- a breech presentation
- when infection or illness, such as HIV or genital herpes, could be passed to the baby during a vaginal birth.
In the US, nearly one-third of all babies arrive via cesarean delivery. Once a person has had a cesarean birth, the odds increase that any subsequent babies will be born that same way. Only 13% of people who have a cesarean will go on to have a VBAC. This matters, because recovery time is longer and the risk of complications is much higher with cesarean births.
Why is trying for a VBAC helpful?
Not everyone who has a cesarean can safely have a VBAC, so check with your doctor about your particular situation. For example, VBAC is usually not recommended for those who have had more than two previous cesarean births.
VBAC does have many benefits, including shorter recovery time and less risk of bleeding, infection, blood clots, and injury to other organs. If you are hoping to have several children in the future, a VBAC also reduces the risk of problems with the placenta — which nourishes the fetus –– during later pregnancies.
How do doctors calculate the likelihood of successful VBAC?
In 2007, the Maternal-Fetal Medicine Units (MFMU) Network created a calculator to estimate a pregnant person’s chances of having a successful VBAC. The calculations took into account many factors believed to influence success:
- age, height, and weight
- whether the previous cesarean delivery was done because dilation of the cervix significantly slowed or stopped, or labor stalled during the pushing phase (the medical terms are arrest of dilation or descent)
- whether a person was being treated for high blood pressure before pregnancy.
Importantly, the original calculator also factored in race and ethnicity. It specifically asked whether the pregnant person was either "African American" or "Hispanic," assigning a lower likelihood of success than it did if the person was white.
Health disparities buried in the original calculator
A high VBAC score (>70%) suggested a high likelihood that vaginal birth would be successful. Selecting yes to "African American" or "Hispanic" instantly lowered the VBAC score for a given patient. Thus, a physician counseling people with similar health histories might recommend against a VBAC for a Black or Hispanic person, while recommending that a white person try for a VBAC — a harmful, self-perpetuating cycle.
In the US, rates of cesarean births are higher among people who are Black or Hispanic than among their white counterparts (36% vs. 31%). This disparity is due to several factors, including implicit bias and racism within the healthcare system. Black women are more than three times as likely to die in childbirth as their white peers. Infant mortality is three times as high among Blacks compared with whites. And cesarean births can contribute to these disparities due to much higher risk for complications than vaginal births, including bleeding, infection, longer recovery time, blood clots, and abnormal placental development in future pregnancies.
New calculator no longer uses race and ethnicity
A new calculator (note: automatic download) released earlier this year eliminates race and ethnicity as factors in estimating a pregnant person’s likelihood for successful VBAC. Research shows the accuracy of predictions made by both calculators is similar, even though the newer model no longer uses race and ethnicity as variables.
Some aspects of the calculations remain unchanged. Both the original and newer calculators predict greater success for VBAC among people who are taller and those who have already had a vaginal birth (particularly after a cesarean birth).
A successful vaginal birth after cesarean delivery is predicted to be less likely among people who had one or more of the following:
- older age
- heavier weight
- a prior cesarean birth done for labor stalling out
- a history of high blood pressure before pregnancy.
Of course, even the newer calculator is far from perfect. Further research needs to be done with larger groups of people of various ages, races, and medical backgrounds to better understand what makes a person more or less likely to have a successful VBAC. Further, this calculator is just one of the tools that physicians should use in a shared decision-making process with people who are pregnant to help decide the type of birth. Importantly, however, taking race and ethnicity out of the calculation is a step toward leveling the playing field, and toward eliminating racial and ethnic disparities in maternal health.
How can you maximize your chances of having a vaginal birth after a cesarean birth?
If you are interested in having a VBAC, be sure to talk to your obstetrical provider early in your pregnancy. Together with your provider, you can input your information into the calculator and discuss the results. This will help you to better understand your chances of success based on your personal situation. Asking your obstetrician to review with you your individual risks and benefits of VBAC versus a repeat cesarean delivery can help you to decide which type of birth is best for you.
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