The Latest Best Evidence on the Safety of VBAC


Henci Goer and Amy Romano have recently published their much awaited book,Optimal Care in Childbirth: The Case for a Physiologic Approach. Their research, based on the best available evidence, makes a strong case for supporting women who want to plan a VBAC.

The most valuable aspect of their book is the fact that they have selected high quality studies that truly compare the benefits and risks of elective repeat cesarean (not medically necessary) with planned VBAC. They have only included well-designed studies that took into account confounding factors, that is, factors that can lead to a misinterpretation of results.

The authors clearly show that some studies published in respected journals may in fact reach mistaken conclusions and confirm that the current, restrictive guidelines for VBAC  are not based on sound evidence.

In the interest of clarifying some of the confusion and misinformation regarding VBAC, here are the facts regarding VBAC based on Goer’s and Romano’s research in Chapter 6 of their book.

Who Can Labor for a VBAC?

Over 95% of women with a prior cesarean can labor safely for a VBAC without any uterine scar problems.

  • Women with more than one prior cesarean
  • Women with a single layer uterine closure
  • Women with a low vertical uterine scar
  • Women with a prior pre-term cesarean.
  • Women with a short inter-delivery interval (< 18 months since the prior birth)
  • Women of older maternal age.
  • Women with an anticipated macrosomic (more than 4000g) baby
  • Women whose pregnancy is past their due date

What are the odds that a woman who wants to labor after a prior cesarean will actually have a VBAC? 

On average the VBAC rate is 74%, but care during labor makes a difference. With usual management, studies report VBAC rates in women with no prior vaginal births ranging from 61% to 72%. With physiologic care, that is, care that supports the natural unfolding of the labor process, a study reported a VBAC rate of 81%. This means that somewhere between 9 and 20 more women with no prior vaginal births will have a VBAC with physiologic care than with usual management.

Most women with a prior cesarean will give birth vaginally, including women with the following conditions:

  • More than one prior cesarean
  • Having had a prior cesarean for:
    • Dystocia (delay in progress)
    • Macrosomia, a baby weighing more than 4000g ( 8lb. 13oz)
    • Older age
    • High body mass index (BMI)
    • Longer pregnancy duration

Women are more likely to have a VBAC if:

  • They have had a prior vaginal birth either before or after the cesarean.
  • Labor begins on its own. One reason heavier women, women carrying bigger babies, and women who are past their due date are more likely to have a repeat cesarean is that they are more likely to have labor induced.
  • They are given physiologic care-supportive of the normal process of labor with minimal use of interventions.

With proper care the risk for a scar rupture can be as low as 0.5% or 1 in 200 healthy women laboring for a VBAC.

The likelihood of a symptomatic scar separation during labor is dependent on the type of care provided to women during surgery and when laboring for a VBAC. To lower the risk for a potential scar rupture:

  • Physicians should use double-, not single–layer, suturing when closing the uterine incision.
  • Avoid inducing or augmenting labor.
  • Misoprostol should not be used for inducing labor in women with a prior cesarean scar.
  • Oxytocin should not be given to induce labor with an unripe cervix.
  • Women undergoing cervical ripening before induction should be given sufficient time for this process (longer than 40 hours).
  • Labor should not be augmented unless the fetal head is engaged in the pelvis and the cervix is dilated 3 or more centimeters.
  • Allow 12 hours between doses of PGE2 (dinoprostone) for cervical ripening and induction.
  • Women with more than one prior cesarean should not be given PGE2.
  • Allow 40 minutes before increasing the oxytocin dose.

No evidence establishes benefits in VBAC labors for the following practices, but they introduce potential harms.

  • Early admission to the labor and delivery unit
  • Routine use of I.V.s
  • Use of an intra-uterine pressure catheter
  • Forbidding food and water (NPO)
  • Establishing a time limit for women to reach full dilation and complete second stage
  • Manually exploring the uterus for scar separation after a vaginal birth

However, electronic fetal monitoring is a reliable indicator of a uterine scar rupture. Over 90% of the time a uterine scar rupture is detected by abnormal fetal heart tones (bradycardia) as documented by electronic fetal monitoring.

What are the advantages for mothers of planning a VBAC?

Accumulating cesarean surgeries increases the likelihood of:

  • Placenta previa, placenta accreta, and having the two in combination
  • Severe bleeding
  • Hysterectomy
  • Maternal admission to ICU
  • Maternal need for postoperative assistance with breathing
  • Thromboembolism
  • Ileus
  • Operative injuries
  • Adhesions

In contrast, having a VBAC decreases the risk of uterine rupture in future VBACs and increases the odds of having another vaginal birth thereby avoiding the risks of additional surgery.

For babies, accumulating cesarean surgeries increases the likelihood of:

  • Preterm birth and subsequent complications
  • Breathing difficulties
  • Admission to NICU

What are the trade-offs between having a VBAC and an elective repeat cesarean?

Although the rates are low, elective repeat cesarean increases the odds of maternal mortality. Twenty-one more women per 100,000 having elective repeat cesareans die than women planning a VBAC.

The differences is small, but 4 more perinatal deaths (deaths during labor or in the days after birth) per 10,000 occur with planned VBAC than with planned repeat cesarean. However, looking at neonatal deaths (deaths in the first four weeks after birth), studies disagree. One study reported rates of 11 per 10,000 with planned VBAC versus 5 per 10,000 with planned repeat cesarean but two others reported identical or nearly identical rates of 7 to 8 per 10,000.

Goer and Romano are optimistic that women have an excellent chance of having a VBAC when given proper care.

…a woman laboring in a low-stress environment surrounded by care providers who are relaxed and confident of her ability to give birth, who make decisions collaboratively with her, and who help her deal with any fears and anxieties is more likely to do well in labor and progress to vaginal birth than a woman who feels she needs to be in defensive mode or who feels unsafe, doubtful, or frightened.

* The information provided in this blog post is based on Chapter 6, “The Case Against Elective Repeat Cesarean,” of Goer’s and Romano’s book, Optimal Care in Childbirth: The Case for a Physiologic Approach (p 95-128).


For additional evidence-based information on the impact of cesarean section see Childbirth Connection’s just published report, Vaginal or Cesarean Birth: What Is At Stake for Mothers and Babies? A Best Evidence Review.