Should You Plan a VBAC or a Repeat Cesarean?

by | Feb 14, 2023 | VBAC (Vaginal Birth after Cesarean)

A study made a stir in the medical obstetric news recently with the alarming finding that planned vaginal birth after cesarean (VBAC) was associated with a greater than two-fold increased risk of having surgery for pelvic floor dysfunction compared with elective repeat cesarean (ERC).7 One medical news aggregator ran a summary of the study under the title “Should Women Attempt Vaginal Birth after Cesarean Delivery?”

Should this study’s results give you pause if you’re considering VBAC? Maybe, maybe not.

Follow along with me while I first zoom in to deconstruct the study and then zoom out to consider the bigger picture of planned VBAC versus ERC in general. Hopefully, that will allow you to determine how much weight to give this study in making your decision. Then, as usual, I’ll wrap up with practical applications for what you have learned.

What’s the Gist of the Study?

Conducted in Scotland, investigators collected a population of 47,414 women who had had one or more cesareans and went on to have one or more subsequent singleton, term (37-41 weeks) births between 1983 and 1996. They followed the group through 2016 to track how many women had surgery for pelvic floor dysfunction in the ensuing years according to whether they planned VBACs or had ERCs. Women could have had vaginal births before entry into the study so long as they also had at least one cesarean.

As I said, researchers found that women who planned VBAC were more than twice as likely (hazard ratio: 2.4) to have pelvic floor surgery to remedy urinary incontinence or uterine prolapse during the roughly 30-year follow-up time period. Furthermore, the excess risk for pelvic floor surgery was limited to women who had VBACs. Women whose labors ended in cesareans had similar rates compared with women having ERC.

A 2.4-fold increased risk of pelvic floor surgery seems concerning, but let’s see what this actually means because with ratios, the absolute percentages vary according to the baseline numbers. A hazard ratio of 2.4 could mean going from, say, 20 percent to 48 percent, or a difference of 28 more women in every 100 planning VBAC having pelvic floor surgery, or it could mean going from 1 percent to 2.4 percent, or a difference less than 2 more women per 100 planning VBAC, which is a very different story. So our first question becomes:

What is the magnitude of the difference in the Scottish study?

In this case, it means that a cumulative rate of a little over 2 percent of women having ERCs had pelvic floor surgery over the ensuing 30 years compared with approaching 6 percent of women planning VBAC. (The authors don’t provide the exact percentages; I’m estimating them from a graph.)

It turns out, though, that the Scottish study isn’t the only word on the issue.

A Swedish study compared women having only vaginal births with women having only cesarean deliveries.16 Like the Scottish study, it was large, compared surgery for pelvic floor dysfunction for cesarean versus vaginal delivery, and followed participants over a similar timespan. In contrast to the Scottish study, though, the Swedish study reported a pelvic floor surgery rate of 3.4 percent in women having vaginal births compared with the Scottish study’s nearly 6 percent.

A 3.4 percent probability versus a nearly 6 percent probability might matter to you in making your decision, but the difference raises a second question: “Which number should you use in your risk versus benefit calculation?” And that question leads to a third question: “What might explain that difference?” To this last question, the Swedish study has possible answers:

  • Surgery rates for urinary incontinence or pelvic floor prolapse increased with increasing numbers of vaginal births. In the Scottish study, 39 percent of women planning VBAC had already had one or more vaginal births prior to study entry. This means that the Scottish study’s pelvic floor surgery rate may not apply if you have no prior vaginal births.  
  • Having an instrumental vaginal delivery increased the probability of surgery for urinary incontinence or pelvic floor prolapse compared with spontaneous vaginal birth. If Scottish obstetricians were more likely to resort to instrumental vaginal delivery than Swedish ones, this could have affected rates of pelvic floor surgery down the line.

We know, too, of other elements of vaginal birth management that can adversely affect the pelvic floor:22, 25, 26

  • Directing women to hold their breaths and push as long and hard as they can.
  • Having women push lying flat or nearly flat on their backs.

In other words, the numbers in the Scottish study cannot be taken as absolute because the incidence of pelvic floor dysfunction varies according to labor management practices. So, while number of vaginal births is a factor, lower pelvic floor surgery rates than those reported in the Scottish study are achievable with optimal VBAC management. That knowledge might shift the balance when considering whether to plan VBAC or repeat cesarean.

That brings us to the other half of this post: the tradeoffs between planned VBAC and ERC.

VBAC Versus ERC: The Bigger Picture

In the interest of transparency, let me start by saying I am pro VBAC. This isn’t necessarily a drawback, though, for two reasons: First I can counterbalance what you may have been hearing from people who are anti VBAC, and second, I will explain what I think, why I think it, and provide the data behind my thinking. That puts you in a good position to decide what you think.

So that we’re comparing apples to apples, I’m only going to address VBAC and repeat cesarean outcomes that, like pelvic floor dysfunction after vaginal birth, have potential ongoing consequences. That is, I’m not going to discuss adverse outcomes that once cured or healed, are over and done.

Planned VBAC Versus ERC: One Cesarean, No Prior Vaginal Births

Let’s start with the choice between planned VBAC and ERC for someone who has had one cesarean and no prior vaginal births.

  • Adverse maternal consequences:
    • Planned VBAC:
      • Surgery for pelvic floor dysfunction:16 fewer than 1 percent of women having two cesareans versus 3 percent of women having one vaginal birth according to the Swedish study. Favors ERC.
    • ERC:
      • Dense adhesions (internal scarring):11 43 percent of women after two cesareans versus 24 percent after one cesarean followed by a vaginal birth. (Vaginal birth poses zero risk of accumulating additional internal scarring.) Dense adhesions increase the probability of experiencing chronic pelvic pain (my sources don’t report the percentage experiencing chronic pain, only that dense adhesions are associated with increased likelihood of experiencing it) and of injury to internal organs during any future pelvic surgeries—not just future cesareans.11, 20 The probability of dense adhesions will vary according to the percentage of women planning VBAC who have unplanned repeat cesareans. VBAC management plays a role here too in that repeat cesarean rates with one cesarean and no prior vaginal births range from 19 percent to 39 percent.3, 9 Favors VBAC.
      • Hysterectomy:8, 11 3 to 4 women per 1000 at second cesarean versus 1 per 1000 with planned VBAC. Favors VBAC.
      • Maternal mortality:28 28 per 100,000 at ERCs versus 7 per 100,000 with planned VBAC. None of the deaths in the planned VBAC group were caused by the scar giving way in a VBAC labor. Favors VBAC.

What about the baby?

  • Adverse consequences for the baby
    • Planned VBAC:
      • Abnormal neurologic symptoms at birth:28 0 per 10,000 ERCs versus 8 per 10,000 planned VBACs. As with pelvic floor dysfunction, however, this outcome depends on labor management as well. As you would expect, the majority of cases occurred in labors in which the uterine scar gave way, but some instances of the scar giving way might have been avoided with less use of oxytocin. Scar rupture incidence rates were 4 per 1000 when labor started on its own, 9 per 1000 in labors made stronger (augmented) with oxytocin, and 10 per 1000 with induced labor.15 Also, not all babies who display abnormal neurologic symptoms at birth will suffer permanent impairment. Its probability depends on the severity of the injury,4 so at least some, if not many babies, will make a full recovery. Favors ERC but we don’t know how many cases might have been avoided or how many resulted in permanent injury.
      • Perinatal mortality: NO DIFFERENCE! The great fear with planned VBAC is death during labor or the newborn period; however, large studies report similar rates of perinatal death with planned VBAC compared with ERC.8, 17, 28 Favors neither.

Conclusion: With one prior cesarean and no prior vaginal births, severe adverse outcomes are rare on both sides, and the odds of experiencing problems arising from pelvic floor weakness versus those arising from dense adhesions probably cancel each other out.

There are, however, two major differences: the adverse effects of planned VBAC vary with management practices, but the adverse effects of repeat cesarean are unavoidable because they are inherent to having surgery. In addition, symptoms of pelvic floor weakness can be relieved or improved by such strategies as engaging in specialized exercises to strengthen the pelvic floor or losing weight,2, 6, 12, 29, 31 and failing all else, by pelvic floor surgery. Nothing can be done to mitigate the adverse effects of internal surgical scarring.

This brings us to the next question: What if you have already had a vaginal birth or are planning on having more than two children?

Planned VBAC Versus ERC: Two or More Prior Vaginal Births Versus Two or More Prior ERCs

If you have already had a vaginal birth or you anticipate having a larger family than two children—and even if you don’t, as someone who planned on two children and has three, I suggest you consider this possibility—the picture changes. Here’s why:

  • If you have had a VBAC or you had a vaginal birth or births before the cesarean, you have a high probability of having uneventful vaginal births in future pregnancies. The probability of VBAC in future pregnancies ranges from 90 to 97 percent with a prior VBAC9, 30 and from 79 to 95 percent with vaginal birth preceding the cesarean.9
  • As the number of cesareans goes up, so does the incidence of severe and life-threatening complications in succeeding pregnancies for both mother and child. The main culprit is the increasing incidence of abnormal placental attachment with increasing number of cesareans:
    • Placenta previa (placenta partially or completely overlays the cervix, the neck-like opening to the uterus):11
      2 percent with two prior cesareans
      3 percent with more than two prior cesareans
    • Placenta accreta (placenta grows into the muscular layer of the uterus):11
      6 per 1000 with two prior cesareans
      21 per 1000 with three prior cesareans
    • Placenta accreta in women with placenta previa:11
      23-47 percent with two prior cesareans
      35-61 percent with three prior cesareans

Let’s look again at planned VBAC, this time with at least one prior VBAC or vaginal birth versus two or more cesareans:

  • Adverse maternal consequences:
    • Multiple Vaginal Births:
      • Surgery for pelvic floor dysfunction:16 fewer than 1 percent of women having cesareans versus 7 percent of women having three or more vaginal births according to the Swedish study.
        Favors ERC.
    • Two or more cesareans:
      • Dense adhesions:11
        43 percent of women after two cesareans
        48 percent of women after three cesareans
        Because of adhesions, the incidence of operative injury increases with additional cesareans. In particular, the incidence of bladder injury is 1 per 1000 with one cesarean versus 3 per 1000 after two.11
        Favors VBAC
      • Hysterectomy:11
        1 percent of women after two prior cesareans
        2 percent of women after three prior cesareans
        Favors VBAC
      • Maternal mortality:27
        49 per 100,000 with two or more prior cesareans (The U.S. maternal mortality rate overall was 20 per 100,000 in 2019.)13
        Favors VBAC
      • Hysterectomy in women with placenta previa:11
        45 percent of women after two prior cesareans
        50-67 percent of women after 3 or more prior cesareans
        Favors VBAC
      • Hysterectomy in women with placenta accreta:14
        52 percent
        Favors VBAC
      • Maternal mortality in women with placenta accreta:14
        50 per 100,000
        Favors VBAC
  • Adverse consequences for the baby
    • Multiple Vaginal Births:
      • Abnormal neurologic symptoms at birth:28 Having a VBAC decreases the incidence of the scar giving way from 8 per 1000 with no previous VBAC to 4 per 1000 with one previous VBAC, and there is no upward trend with additional VBAC labors.18 That necessarily means decreased probability of the baby experiencing abnormal neurologic symptoms at birth compared with no previous VBAC since the scar opening is the main precipitating event. Note, though, that 4 per 1000 with previous VBAC is the same incidence as with no previous VBAC and laboring spontaneously, that is, no labor induction or augmentation of labor with oxytocin. To repeat what I’ve said before, VBAC management plays a role in outcomes. Favors VBAC
    • More than 1 additional cesarean:
      • Preterm birth in women with placenta previa:
        35-42 percent delivered at less than 37 weeks gestation10, 21
        7-15 percent delivered at less than 32 weeks gestation10, 21
        Favors VBACs
      • Preterm birth in women with placenta accreta:19
        59 percent delivered at less than 37 weeks gestation
        5 percent delivered at less than 30 weeks gestation
        Favors VBACs
      • Perinatal mortality: I don’t have data on this. Surely, however, the increase in severe and life-threatening adverse outcomes in mother and child with increasing numbers of cesareans increases the probability of perinatal death whereas the decreased risk of scar ruptures with multiple VBACs does the opposite.
        Favors VBACs.

Conclusion: To recap, accumulating vaginal births increases the likelihood of having surgery for pelvic floor dysfunction. On the other hand, the odds of the scar giving way diminish after the first VBAC and don’t rise again with succeeding VBACs, which lowers the probability of the baby experiencing severe morbidity or mortality. In contrast, mostly because of increased incidence of abnormal placental attachment, the risk of severe adverse outcomes increases with accumulating cesareans for both mother and child. Furthermore, surgery provides a remedy for severe pelvic floor dysfunction, but we have no remedy for the severe consequences of accumulating cesareans.

To my mind, even a small increased risk of severe adverse outcomes with accumulating cesarean surgeries tips the balance toward planning VBAC at that initial fork in the road, especially in light of the diminished risk to the baby with additional VBACs. As Carol Sakala put it:24

As many women will have additional children, future childbearing is difficult to predict, and hazards increase as the number of previous cesareans grows, it would be wise for women without a clear and compelling need for cesarean section in the present pregnancy to avoid the extra risks of surgery and to get off the repeat cesarean track.

The Take-Away

What can be gleaned from all this? If you want to plan an ERC, the obstetrician’s practices and policies don’t much matter. Surgery is surgery, so any obstetrician should be competent to do the job. If you want to plan a VBAC, however, practices and policies are crucial to achieving optimal outcomes, which means finding a care provider who is enthusiastic about VBAC and skilled at managing them.

Unfortunately, finding a VBAC care provider who fits these criteria may not be easy. For one thing, many hospitals and practitioners don’t offer VBAC. Their rationale is that VBAC labors aren’t safe in a hospital that isn’t staffed to handle obstetric emergencies 24/7. But emergencies can arise in labors other than those after a prior cesarean. If a hospital isn’t safe for a VBAC labor, it isn’t safe for any labor.

Be that as it may, a straight up “no,” at least, lets you know where they stand. More problematic is the use of “bait-and-switch”: obstetricians who agree to a VBAC at your initial visit, but as the due date approaches, become more and more negative on the idea. They start warning about risks, add more stringent eligibility requirements, or even outright refuse a VBAC if they can’t convince you to change your mind. At this point, the due date is close enough that it is emotionally and practically extremely difficult, if not impossible, to find someone else. That I can help with. Here are some interview questions to help you determine who’s genuinely pro VBAC:

  • What percentage of your patients/clients* with prior cesareans plan VBAC? Few people with prior cesareans have conditions that render them ineligible for VBAC. While not everyone will opt for VBAC, a low percentage tells you that this care provider isn’t truly encouraging.
  • What percentage of your patients/clients* who plan VBACs have VBACs? Numbers in the mid-70 percents are readily achievable.11
  • What are your eligibility criteria and policies for VBAC labors? Regarding candidacy, unless there is a contraindication to labor—and, by the way, two prior cesareans isn’t one in itself1— the practitioner should be open to VBAC. As for policies, with the possible exception of continuous fetal monitoring, we have evidence of harm and no evidence of benefit for admission in early labor, routine IV (a saline lock is a good compromise because it doesn’t interfere with mobility), confinement to bed, and preset time limits for making progress. Specific to VBAC, internal contraction monitoring has not been shown to identify that the scar has given way.5, 23
  • Do all of the doctors/midwives in your group feel as you do about VBAC? If not, how can I ensure that I will be attended by someone who does? Most practitioners work in group practices and rotate call among its members. Practice members may vary in their attitude toward VBAC and how they manage one.

*Doctors have “patients”; midwives have “clients,” which emphasizes both that pregnancy isn’t an illness and that women take an active role in their care and in decision making.

References

  1. ACOG. Practice Bulletin No. 184: Vaginal Birth After Cesarean Delivery. Obstet Gynecol 2017;130(5):e217-e33.
  2. Aune D, Mahamat-Saleh Y, Norat T, et al. Body mass index, abdominal fatness, weight gain and the risk of urinary incontinence: a systematic review and dose-response meta-analysis of prospective studies. BJOG 2019;126(12):1424-33.
  3. Cheyney M, Bovbjerg M, Everson C, et al. Outcomes of care for 16,924 planned home births in the United States: the Midwives Alliance of North America statistics project, 2004 to 2009. J Midwifery Womens Health 2014;59(1):17-27.
  4. de Vries LS, Cowan FM. Evolving understanding of hypoxic-ischemic encephalopathy in the term infant. Semin Pediatr Neurol 2009;16(4):216-25.
  5. Devoe LD, Croom CS, Youssef AA, et al. The prediction of “controlled” uterine rupture by the use of intrauterine pressure catheters. Obstet Gynecol 1992;80(4):626-9.
  6. Dumoulin C, Cacciari LP, Hay-Smith EJC. Pelvic floor muscle training versus no treatment, or inactive control treatments, for urinary incontinence in women. Cochrane Database Syst Rev 2018;10(10):CD005654.
  7. Fitzpatrick KE, Abdel-Fattah M, Hemelaar J, et al. Planned mode of birth after previous cesarean section and risk of undergoing pelvic floor surgery: A Scottish population-based record linkage cohort study. PLoS Med 2022;19(11):e1004119.
  8. Gilbert SA, Grobman WA, Landon MB, et al. Elective repeat cesarean delivery compared with spontaneous trial of labor after a prior cesarean delivery: a propensity score analysis. Am J Obstet Gynecol 2012;206(4):311 e1-9.
  9. Goer H. The case against elective repeat cesarean. In: Goer H., Romano A., eds. Optimal Care in Childbirth: The Case for a Physiologic Approach. Seattle, WA: Classic Day Publishing; 2012.
  10. Grobman WA, Gersnoviez R, Landon MB, et al. Pregnancy outcomes for women with placenta previa in relation to the number of prior cesarean deliveries. Obstet Gynecol 2007;110(6):1249-55.
  11. Guise JM, Eden K, Emeis C, et al. Vaginal birth after cesarean: new insights. Evid Rep Technol Assess (Full Rep) 2010(191):1-397.
  12. Hagen S, Stark D, Glazener C, et al. Individualised pelvic floor muscle training in women with pelvic organ prolapse (POPPY): a multicentre randomised controlled trial. Lancet 2014;383(9919):796-806.
  13. Hoyert DL. Maternal mortality rates in the United States, 2019. In: Health E-Stats: National Center for Health Statistics; April 2021.
  14. Jauniaux E, Bunce C, Gronbeck L, et al. Prevalence and main outcomes of placenta accreta spectrum: a systematic review and meta-analysis. Am J Obstet Gynecol 2019;221(3):208-18.
  15. Landon MB, Hauth JC, Leveno KJ, et al. Maternal and perinatal outcomes associated with a trial of labor after prior cesarean delivery. N Engl J Med 2004;351(25):2581-9.
  16. Leijonhufvud A, Lundholm C, Cnattingius S, et al. Risks of stress urinary incontinence and pelvic organ prolapse surgery in relation to mode of childbirth. Am J Obstet Gynecol 2011;204(1):70 e1-7.
  17. Menacker F, MacDorman MF, Declercq E. Neonatal mortality risk for repeat cesarean compared to vaginal birth after cesarean (VBAC) deliveries in the United States, 1998-2002 birth cohorts. Matern Child Health J 2010;14(2):147-54.
  18. Mercer BM, Gilbert S, Landon MB, et al. Labor outcomes with increasing number of prior vaginal births after cesarean delivery. Obstet Gynecol 2008;111(2 Pt 1):285-91.
  19. Miller DA, Chollet JA, Goodwin TM. Clinical risk factors for placenta previa-placenta accreta. Am J Obstet Gynecol 1997;177(1):210-4.
  20. Moro F, Mavrelos D, Pateman K, et al. Prevalence of pelvic adhesions on ultrasound examination in women with a history of Cesarean section. Ultrasound Obstet Gynecol 2015;45(2):223-8.
  21. Olive EC, Roberts CL, Algert CS, et al. Placenta praevia: maternal morbidity and place of birth. Aust N Z J Obstet Gynaecol 2005;45(6):499-504.
  22. Prins M, Boxem J, Lucas C, et al. Effect of spontaneous pushing versus Valsalva pushing in the second stage of labour on mother and fetus: a systematic review of randomised trials. BJOG 2011;118(6):662-70.
  23. Rodriguez MH, Masaki DI, Phelan JP, et al. Uterine rupture: are intrauterine pressure catheters useful in the diagnosis? Am J Obstet Gynecol 1989;161(3):666-9.
  24. Sakala C, Corry MP. Evidence-Based Maternity Care: What It Is and What It Can Achieve. New York: Milbank Memorial Fund; 2008.
  25. Schaffer JI, Bloom SL, Casey BM, et al. A randomized trial of the effects of coached vs uncoached maternal pushing during the second stage of labor on postpartum pelvic floor structure and function. Am J Obstet Gynecol 2005;192(5):1692-6.
  26. Serati M, Di Dedda MC, Bogani G, et al. Position in the second stage of labour and de novo onset of post-partum urinary incontinence. Int Urogynecol J 2016;27(2):281-6.
  27. Silver RM, Landon MB, Rouse DJ, et al. Maternal morbidity associated with multiple repeat cesarean deliveries. Obstet Gynecol 2006;107(6):1226-32.
  28. Spong CY, Landon MB, Gilbert S, et al. Risk of uterine rupture and adverse perinatal outcome at term after cesarean delivery. Obstet Gynecol 2007;110(4):801-7.
  29. Subak LL, Wing R, West DS, et al. Weight loss to treat urinary incontinence in overweight and obese women. N Engl J Med 2009;360(5):481-90.
  30. van der Merwe AM, Thompson JM, Ekeroma AJ. Factors affecting vaginal birth after caesarean section at Middlemore Hospital, Auckland, New Zealand. N Z Med J 2013;126(1383):49-57.
  31. Wing RR, West DS, Grady D, et al. Effect of weight loss on urinary incontinence in overweight and obese women: results at 12 and 18 months. J Urol 2010;184(3):1005-10.

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