Vaginal Birth after Cesarean (VBAC) Risks Versus Repeat Cesarean

A cesarean section delivery (aka “c-section”) is an invasive birth surgery in which a doctor reaches into a hole cut into a mother’s abdomen to deliver an infant. Not surprising, c-sections are associated with a number of birth injuries to mother and child.

Cesarean birth injury complications include: risks of infection (including sepsis), painful scar tissue (“adhesions”), blood clots (“pulmonary embolisms”), and all the dangers associated with anesthesia, including a risk of choking on vomit, heart failure, and coma. C-sections also increase the chance of both needing c-sections for future births and of hysterectomies.

Mothers considering delivering their next child through vaginal birth after cesarean, or “VBAC,” need to weigh the birth risks of uterine rupture and positives of vaginal birth against the benefits and dangers of repeat cesarean section. The risks are about equal for birth injury if attended by a negligent doctor or inattentive hospital staff.

Reasons for Having a VBAC

It is little wonder that many mothers choose not to have a cesarean section, especially if they have had a c-section previously. This invasive abdominal surgery, like any serious surgery, increases risks of infection, necessitates anesthesia, and results in significant blood loss—any of which can result in birth injury to mother or newborn. C-sections also increase the time and cost of one’s hospital stay. Avoiding a c-section with a VBAC (pronounced VEEback) also offers a number of more natural birth options that may reduce the risk of birth injury in hospitals.

Need for re-hospitalization, traumatic birth injury, and death are reduced for vaginal births than for surgical intervention. Fortunately, women who attempt a vaginal birth after cesarean are most likely (70-80%) to succeed without surgery. The greatest danger VBAC mothers face is of the internal scar from their c-section(s) opening in a dangerous event called uterine rupture.

Uterine Rupture Danger for Vaginal Birth after Cesarean (VBAC)

While uterine rupture can occur during any form of birth, uterine ruptures are about twice as likely in VBAC than in cesarean births. Less than one in a hundred VBACs result in a uterine rupture. Of these ruptures, one in twenty infants die. Mothers have a higher risk of injury from infection if VBAC birth is tried but a cesarean section delivery (because of a uterine rupture or other complications) is required.

Uterine rupture makes VBAC a birth injury risk equal to a cesarean section. The risk of birth injury to an infant from a uterine rupture during vaginal birth after cesarean is about equal to the risks the mother faces when undergoing a c-section, though both birth procedures carry potential risks to both mother and child, such as severe blood loss that can cause cerebral palsy . (Click to read this Slate article by David Dobbs who discusses his and his wife’s decision after weighting VBAC’s risks.)

This risk for cesarean section increases with every c-section birth a mother has and for women 35 and older. Another factor increasing the likelihood of uterine tears during VBAC is chemically induced labor. Prostaglandin labors have been found to increase uterine ruptures by about fifteen times. But the greatest factor for safe VBAC is how the previous c-section was performed.

Previous C-Section Type Influences VBAC Rupture

The way the doctor cut the cesarean also affects the risk of VBAC rupture. The three types of incisions are:

  • High vertical cesarean section (aka “classical cesarean section”)
  • Low transverse cesarean section
  • Low vertical cesarean section

Low vertical (up and down cut) and low transverse (horizontal cut) cesarean sections occur in the lower, thinner part of the uterus where scarring is less likely to show. These low c-sections have nearly replaced high vertical c-sections for this reason.

High vertical cesarean sections also carry a significantly higher risk of VBAC rupture. High vertical c-sections were responsible for the idea that “once a cesarean, always a cesarean.” Once thought extinct, this outdated saying is gaining new currency with a new generation of obstetricians who demand repeat cesareans for mothers.

Why Hospital Doctors Discourage VBAC

Vaginal births after cesarean, despite an increase demand, have fallen by over half in the last ten years. The reason appears not to be doctors’ birth injury fears but rather a changing of guidelines in protecting a laboring mother—guidelines doctors and hospital staff find inconvenient

In 2004, American College of Obstetricians and Gynecology (ACOG), the main organization for establishing guidelines and which 9 out of 10 birth doctors are part of, changed its wording concerning VBAC. Doctors were no longer to be “readily” available but “immediately” available. This word change meant that the birth doctor and anesthesiologist have to be somewhere in the hospital while the VBAC mother is in labor in case she suffers a uterine rupture and/or needs a cesarean section delivery.

This single word has banned VBAC in many medical institutions.

Doctors who perform VBAC are often pressured by hospital staff and other doctors to make another cesarean the only option available to a woman, as detailed in this USA Today story on the battlelines over VBAC and c-sections.2

If You Are Considering VBAC

Couples considering VBAC should consult with their primary physician and/or midwife who can inform them of the most recent research on VBAC and its birth injury risks. As with any major medical consideration, informed consent is required. A mother must be informed of the following four factors:

  • Nature of procedure (what will happen)
  • Dangers (what might go wrong)
  • Alternatives (what options are available)
  • Benefits (what is the best that can be expected versus the alternatives)

Repeat cesarean sections are serious operations that increase the likelihood of birth injuries. Whether you chose to try a VBAC or prefer a repeat cesarean section delivery, this choice should be addressed in a mother’s birth plan.