In VBAC (Vaginal Birth after Cesarean)

cesarean instrument tray

In Part 1 of this two-part series, we looked at the indefensibly high cesarean rate in first-time mothers and how to avoid a cesarean with a first baby. Now, let’s turn to the equally indefensible repeat cesarean rate. 

As I noted in part one, the U.S. cesarean rate has held steady at 1 in 3 women for over a decade.24 While one reason for this is the high rate in first-time mothers, the other is that once women have a first cesarean, they almost all—about nine out of ten of them—go on having repeat cesareans for all subsequent deliveries.24 Mostly, this low number has to do with how few women try for a vaginal birth. This may be because they never knew vaginal birth after cesarean (VBAC) was an option, their doctors talk them out of it, or because their doctors or hospital refuse to allow them.26

In this post, we’ll look at why you might want to plan a VBAC, how likely a VBAC should be, and what you can do to avoid an avoidable repeat cesarean.

Should You Plan a VBAC or a Repeat Cesarean?

The primary argument used to dissuade women from VBAC is that the uterine scar may give way and the consequences will be disastrous for the baby if it does. The commonly quoted percentage of VBAC labors in which this happens is 1%, but according to the research, the true percentage is half that.14 And while an urgent cesarean will almost always be necessary, an adverse outcome for the baby is rare. (“Taking a Deeper Dive” below has the specifics on this.) Moreover, the likelihood of scar rupture is dependent on obstetric management, so, for example, the use of cervical ripening agents and of oxytocin to induce labor or strengthen contractions elevates the risk.

Women may also be told that maternal complications are more likely in VBAC labors than in planned cesareans. This is true for some complications while others are a wash and still others favor planned VBAC. Whichever the case, the serious complications such as blood clots, injury during surgery, need for transfusion, infection, or hysterectomy are uncommon or rare, and differences in occurrence rates are small. (For details, see “Taking a Deeper Dive.”) Furthermore, most adverse outcomes in VBAC labors occur in the labors that end in a cesarean,14, 20 which means the higher the VBAC rate, the better planned VBAC looks and vice versa.

Arguments against VBAC usually stop with the next pregnancy, but any calculation of comparative risks should include the risks of accumulating cesareans because even women planning only two children may change their minds or have an unplanned pregnancy. Once a woman has a VBAC, she will almost always go on having uneventful VBACs, but each successive cesarean increases the risks of severe complications in the next pregnancy and therefore their adverse consequences, consequences that threaten the life of both the baby and the mother. (Again, “Taking a Deeper Dive” has the details.) These include placenta previa (the placenta partially or completely overlays the cervix; the neck-like opening to the uterus); placenta accreta (the placenta grows into and sometimes through the muscular layer of the uterus); the two in combination; and the formation of adhesions (dense internal scar tissue). Add this to the consideration, and the scales tip firmly toward VBAC.

Finally, the benefits of birthing vaginally should be considered. Studies don’t report on this, but differences in the recovery experience such as pain and ability to carry out daily activities undoubtedly favor VBAC over repeat cesarean by a wide margin. This isn’t trivial when you have not only the new baby but another young child or children to be looked after. As with maternal risks, though, potential benefits depend on the likelihood of vaginal birth. This brings us to the next question:

What Are the Odds of Vaginal Birth?

The other main argument used to dissuade women from VBAC is that vaginal birth isn’t likely. National statistics don’t report on what percentage of VBAC labors end in vaginal birth, but a study of 11,000 women with prior cesareans reported a VBAC rate of 84% in a mixed population of women with and without prior vaginal births.18 Based on that study, your odds of vaginal birth should be good—better, in fact, than the odds of vaginal birth in 1st-time mothers by a substantial amount in this country. However, as I said above, women with a vaginal birth either before or after a cesarean rarely need a repeat cesarean at subsequent births. Looking at studies of women with a prior cesarean and no prior vaginal births, VBAC rates range from 61% to 79%, which are still pretty good odds and, again, in the range of vaginal birth rates for 1st-time mothers with typical obstetric management.2, 4-6, 11, 13, 15, 16, 19, 21, 29, 32

That’s not the end of the story, though. As we saw for cesareans in 1st-time mothers in Part 1 of this series, likelihood of VBAC depends far more on the beliefs and policies of the clinician than it does on factors having to do with women or their prior births. How do we know this? Two ways: first, the wide range in rates—61% to 79%—in studies where obstetricians managed labors tells us that something is going on besides differences in the characteristics of the women, and second, as we did with cesareans in 1st-time mothers, we have a comparison coming from a different model of care: Midwives achieved a vaginal birth rate of 81% in women with a prior cesarean and no prior vaginal births,8, 22 or as many as 20 more vaginal births per 100 VBAC labors than obstetricians.

In other words, absent medical reasons for a repeat cesarean, planned VBAC is the better bet but only if you have care providers who truly support VBAC and whose care practices promote safe, vaginal birth.

How Can You Avoid an Avoidable Repeat Cesarean?

Most women with one previous cesarean delivery with a low-transverse incision [the standard type] are candidates for and should be counseled about and offered [VBAC]. . . . Given the overall data, it is reasonable to consider women with two previous low-transverse cesarean deliveries to be candidates for [VBAC]. American College of Obstetricians & Gynecologists1

Let’s assume you’ve decided that you want to go for a VBAC. Despite the American College of Obstetricians & Gynecologists’ recommendation in this quote from its VBAC Practice Bulletin, your first problem is likely to be finding someone who agrees to a VBAC labor at all.26 If you can find someone, your next task is determining whether they genuinely support VBAC. All too many obstetricians agree early in the pregnancy, but as the due date approaches, begin finding more and more qualifying hoops you must jump through or ratchet up pressure to agree to a cesarean. Here are some questions that can help:

  • Will you or someone in your practice be attending my birth? Some hospitals use “laborists,” obstetricians employed by the hospital who manage labors and births there. There’s no point continuing with the rest of these questions if your doctors or midwives won’t be responsible for your care in labor.
  • What percentage of your patients with a prior cesarean plan a VBAC? This number tells you whether this care provider truly encourages VBAC. This should be most of them since few circumstances contraindicate VBAC.
  • What percentage of those who plan a VBAC have a vaginal birth? As we saw above, rates in the mid 80 percents are achievable, but I’d call anything in the mid 70 percents or above acceptable.
  • Do you use a VBAC prediction calculator to advise me about candidacy for VBAC? VBAC prediction scoring systems are in wide use, and in many cases, they are being used to discourage or deny VBAC.30 Obviously, there are factors that would decrease the probability of vaginal birth, but as we saw above, the likelihood of VBAC depends far more on the beliefs and policies of the clinician than it does on factors relating to you or your cesarean, and as with VBAC rates in general, the extreme variability in VBAC rates in women with these factors confirms this. For example, studies have reported VBAC rates ranging from 55% to 72% in high BMI women.14, 33 Certainly, too, denying VBAC altogether based on a low prediction score should send you out the door because it violates your fundamental right to refuse consent to a medical procedure, in this case, cesarean surgery.  
  • Under what circumstances would you recommend a repeat cesarean? These should be serious medical conditions or labor complications, not circumstantial reasons such as having a prior cesarean for slow progress, a baby estimated to be bigger than average, going past your due date, or failing to meet preset time limits for making progress in labor.
  • What are your criteria and policies for VBAC labors? The only difference from care in a non-VBAC labor for which a case can be made is continuous fetal monitoring.  
  • Do all the others in your practice feel as you do about VBAC? If not, how can I ensure that I will be attended by someone who does? Most doctors and midwives are in group practices and rotate who is on call for births. It is entirely possible that some practice members don’t permit VBAC or hedge it about with so many non-evidence-based restrictions that it amounts to the same thing.

For more on the comparative safety of planned VBAC versus repeat cesarean, your individualized likelihood of VBAC, and how to maximize your chances of an uneventful VBAC, see Childbirth U’s masterclass “Vaginal Birth after Cesarean?”

Taking a Deeper Dive

Perinatal mortality and severe morbidity are rare consequences of uterine scar rupture.

Two studies provide information on how commonly scar rupture results in death during labor or in the days following birth. One reported 2 in 17,900 VBAC labors for a rate of 1 per 10,000 (Landon 2004),20 and the other, an analysis of a series of 347 cases of the scar giving way during VBAC labor, reported that 3% resulted in death (Barger 2012),3 so assuming the symptomatic scar separation rate of 5 per 1000 reported in Guise (2010),14 the likelihood of perinatal death related to it would be 1 per 10,000, the same as Landon (2004).

A lesser, but serious, consequence of scar rupture is hypoxic-ischemic encephalopathy (abnormal neurologic signs at birth from oxygen deprivation). A study of the same population as Landon (2004) reported 7 cases in 15,323 VBAC labors for a rate of 5 per 10,000 (Spong 2007).28 The analysis of 347 cases of the scar opening reported that 23% of babies had abnormal neurologic symptoms or seizure (Barger 2012).3 If we assume a symptomatic scar separation rate of 0.5%, then 0.5% x 23% = 0.1% or 1 case of abnormal neurologic signs or seizure per 1000 planned VBACs. Neither study follows up on these babies. The likelihood of permanent impairment depends on severity of the injury (De Vries 2009),10 so at least some, if not many, babies will make a full recovery.

Comparing planned VBAC versus planned repeat cesarean, some serious maternal adverse outcomes rates are similar, some slightly favor planned cesarean, and others slightly favor planned VBAC.

Deep Venous Clot or Pulmonary Embolism (Thromboembolism)

A systematic review (a study of studies on a particular topic) reports that a large, multicenter study found the lowest incidence rate of thromboembolism in women laboring after one cesarean (4 per 10,000) compared with either planned cesarean or labor after multiple cesareans (10 per 10,000 in both cases) (Guise 2010).14

Injury during Surgery

We don’t have any studies reporting on this outcome specifically in the next pregnancy after the first cesarean; however, the systematic review reported similar pooled rates of surgical injury overall between planned VBAC and planned cesarean (Guise 2010).14 Injury was more likely at cesarean during labor. One study reporting specifically on bladder injury found a small, but statistically significant excess, with planned VBAC (5 vs. 4 per 10,000). Another study likewise reported that among women with bladder injuries, more women (64% vs. 22%) had cesareans during labor than planned cesareans.

Transfusion

A large study (25,156 women) in women having the next delivery after a first cesarean found that likelihood of transfusion was greater in women planning VBACs than in women having planned repeat cesarean (3 vs. 2 per 100) (Holm 2012),17 but this is probably because investigators were looking only at the second delivery. The likelihood of hemorrhage goes up with increasing numbers of repeat cesareans. (See “Accumulating cesarean surgeries . . .” below.)

Infection

A study used propensity scoring (a statistical technique used to create groups that differ only according to the exposure of interest) to compare hysterectomy rates in women with one prior cesarean according to whether they planned VBAC or had an elective repeat cesarean (no medical indication for planning a cesarean) (Gilbert 2012).12 All women in the study were at 37 weeks gestation or more with one, head-down baby, and women planning VBAC began labor on their own. Among the 3981 matched pairs of women, endometritis was more frequent with planned VBAC (4% vs. 2%), but the study’s authors point out that the VBAC rate in women planning vaginal birth was only 68% and that with a higher vaginal birth rate, differences in adverse outcomes could be reduced or even disappear.

Hysterectomy

The same study as in the previous section reported on hysterectomy, finding that 2 more women per 1000 had hysterectomies with elective repeat cesarean (3 vs. 1 per 1000) (Gilbert 2012).12

Accumulating cesarean surgeries increases the likelihood of severe adverse outcomes in mothers and babies.

Maternal Death

A study of a large population of U.S. women reported that the maternal mortality rate in women with 1 or more prior cesareans was 63 per 100,000 (15 in 23,841) (Silver 2006).27 Compare this with 13 per 100,000, the U.S. maternal mortality rate during a year that fell within the timeframe of the study (Chang 2003).7 Doubtless some of the excess is because women with life-threatening conditions are more likely to deliver by repeat cesarean, but equally doubtless is that some of the excess is attributable to the risks imposed by current and prior surgeries.

Hysterectomy

All studies cited in a systematic review (a study of studies on a particular topic) reported an increased likelihood of hysterectomy with multiple prior cesareans compared with one (Guise 2010).14 Among studies reporting rates, one study reported 4 more hysterectomies per 1000 with more than 1 vs. 1 prior cesarean (11 vs. 7 per 1000). Another reported 9 more hysterectomies per 1000 with 2 or more prior cesareans vs. 1 prior cesarean (11 vs. 2 per 1000), although this difference did not achieve statistical significance, meaning the difference might have been due to chance. A third study reported hysterectomy rates of 4 per 1000 with one prior cesarean, 9 per 1000 with two, 24 per 1000 with three, 35 per 1000 with four, and 90 per 1000 with 5 or more.

Dense Internal Scar Tissue (Adhesions)

Adhesions make any future cesareans or other abdominal surgery more difficult and more likely to result in operative injury to internal organs or blood vessels. They also may cause chronic pain. The systematic review found increased likelihood of adhesions with increasing numbers of cesareans (Guise 2010).14 One study reported a rate of 26% with one prior cesarean vs. 49% with 2 or more. Another reported a 46% rate with 2 or more prior cesareans. A third study compared women with 3 or more prior cesareans to a control group and likewise reported greater incidence of adhesions in women with 3 or more prior cesareans (18% vs. 3%). Reviewers cite a fourth adhesion study in a different section without reporting details: an adhesion rate of 24% with one prior cesarean, 43% with two, and 48% with 3 or more (Tulandi 2009).31

Injury during Surgery

Several studies report on bladder injury during cesarean surgery with 2 or more prior cesareans compared with 1 prior cesarean (Cook 2013; Makoha 2004; Nisenblat 2006; Silver 2006).9, 23, 25, 27 The rate with 1 prior cesarean ranges from 1 to 3 per 1000 compared with 4 to 13 per 1000 with 2 or more prior cesareans among the studies. The excess with 2 or more prior cesareans ranges from 4 to 10 more per 1000 within the studies. Three of the studies also look at bowel injury (Makoha 2004; Nisenblat 2006; Silver 2006).23, 25, 27 The rate with 1 prior cesarean ranges from 0 to 6 per 10,000 compared with 17 to 20 per 10,000 with 2 or more prior cesareans among the studies. The excess with 2 or more prior cesareans ranges from 9 to 10 more per 10,000 within the studies.

Other Severe Maternal Adverse Outcomes

The likelihood of severe bleeding also rises with number of cesareans according to the systematic review (Guise 2010).14 One study reported transfusion rates of 18 per 1000 with one prior cesarean, increasing to 26 with two, 43 with three, 46 with four, and 146 with 5 or more. Another found higher rates (79 vs. 33 per 1000) of “excessive blood loss” (defined as more than 1000 mL or transfusion of 2 or more units) with 2 or more prior cesareans compared with 1 prior cesarean.

Incidences of other adverse maternal outcomes also rise significantly as the number of prior cesareans increases from one to five or more (Silver 2006).27 These include the need for breathing assistance after surgery (postoperative ventilation) (2 per 1000 rising to 11 per 1000), paralyzed bowel (ileus) (5 per 1000 rising to 34 per 1000), and admission to intensive care (6 per 1000 rising to 56 per 1000).

Adverse Outcomes for the Baby

A study compared outcomes in women with 4 or more prior cesareans with outcomes in women with 1-3 prior cesareans (Cook 2013).9 This was essentially a comparison of 4-5 prior cesareans with 1-2 prior cesareans because only 6 of 94 women had more than 5 prior cesareans in the 4 or more group, and only 6 of 175 women had 3 prior cesareans in the 1-3 prior cesareans group. Compared with the group with fewer prior cesareans, 20 more babies per 100 were born at less than 37 weeks (25% vs. 5%), 6 more per 100 had medical complications (bleeding within the brain, severe jaundice, severe infection, abnormal neurologic symptoms) (8% vs. 2%), and 17 more per 100 were admitted to intensive care (24% vs. 7%).

References

  1. ACOG. Practice Bulletin No. 184: Vaginal Birth After Cesarean Delivery. Obstet Gynecol 2017;130(5):e217-e33.
  2. Agnew G, Turner MJ. Vaginal prostaglandin gel to induce labour in women with one previous caesarean section. J Obstet Gynaecol 2009;29(3):209-11.
  3. Barger MK, Nannini A, Weiss J, et al. Severe maternal and perinatal outcomes from uterine rupture among women at term with a trial of labor. J Perinatol 2012;32(11):837-43.
  4. Cahill AG, Stamilio DM, Odibo AO, et al. Is vaginal birth after cesarean (VBAC) or elective repeat cesarean safer in women with a prior vaginal delivery? Am J Obstet Gynecol 2006;195(4):1143-7.
  5. Cameron CA, Roberts CL, Peat B. Predictors of labor and vaginal birth after cesarean section. Int J Gynaecol Obstet 2004;85(3):267-9.
  6. Caughey AB, Shipp TD, Repke JT, et al. Trial of labor after cesarean delivery: the effect of previous vaginal delivery. Am J Obstet Gynecol 1998;179(4):938-41.
  7. Chang J, Elam-Evans LD, Berg CJ, et al. Pregnancy-related mortality surveillance–United States, 1991–1999. MMWR Surveill Summ 2003;52(2):1-8.
  8. 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.
  9. Cook JR, Jarvis S, Knight M, et al. Multiple repeat caesarean section in the UK: incidence and consequences to mother and child. A national, prospective, cohort study. BJOG 2013;120(1):85-91.
  10. de Vries LS, Cowan FM. Evolving understanding of hypoxic-ischemic encephalopathy in the term infant. Semin Pediatr Neurol 2009;16(4):216-25.
  11. Flamm BL, Geiger AM. Vaginal birth after cesarean delivery: an admission scoring system. Obstet Gynecol 1997;90(6):907-10.
  12. 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.
  13. Goodall PT, Ahn JT, Chapa JB, et al. Obesity as a risk factor for failed trial of labor in patients with previous cesarean delivery. Am J Obstet Gynecol 2005;192(5):1423-6.
  14. Guise JM, Eden K, Emeis C, et al. Vaginal birth after cesarean: new insights. Evid Rep Technol Assess (Full Rep) 2010(191):1-397.
  15. Gyamfi C, Juhasz G, Gyamfi P, et al. Increased success of trial of labor after previous vaginal birth after cesarean. Obstet Gynecol 2004;104(4):715-9.
  16. Hendler I, Bujold E. Effect of prior vaginal delivery or prior vaginal birth after cesarean delivery on obstetric outcomes in women undergoing trial of labor. Obstet Gynecol 2004;104(2):273-7.
  17. Holm C, Langhoff-Roos J, Petersen K, et al. Severe postpartum haemorrhage and mode of delivery: a retrospective cohort study. BJOG 2012;119(5):596-604.
  18. Holmgren C, Scott JR, Porter TF, et al. Uterine rupture with attempted vaginal birth after cesarean delivery: decision-to-delivery time and neonatal outcome. Obstet Gynecol 2012;119(4):725-31.
  19. Kwee A, Bots ML, Visser GH, et al. Obstetric management and outcome of pregnancy in women with a history of caesarean section in the Netherlands. Eur J Obstet Gynecol Reprod Biol 2007;132(2):171-6.
  20. 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.
  21. Landon MB, Leindecker S, Spong CY, et al. The MFMU Cesarean Registry: factors affecting the success of trial of labor after previous cesarean delivery. Am J Obstet Gynecol 2005;193(3 Pt 2):1016-23.
  22. Lieberman E, Ernst EK, Rooks JP, et al. Results of the national study of vaginal birth after cesarean in birth centers. Obstet Gynecol 2004;104(5 Pt 1):933-42.
  23. Makoha FW, Felimban HM, Fathuddien MA, et al. Multiple cesarean section morbidity. Int J Gynaecol Obstet 2004;87(3):227-32.
  24. Martin JA, Hamilton BE, Osterman MJK, et al. Births: Final data for 2018. Natl Vital Stat Rep 2019;68(13):1-46.
  25. Nisenblat V, Barak S, Griness OB, et al. Maternal complications associated with multiple cesarean deliveries. Obstet Gynecol 2006;108(1):21-6.
  26. Sakala C, Declercq E, Turon JM, et al. Listening to Mothers in California. Washington, D.C.: National Partnership for Women & Families; 2018.
  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. Srinivas SK, Stamilio DM, Stevens EJ, et al. Predicting failure of a vaginal birth attempt after cesarean delivery. Obstet Gynecol 2007;109(4):800-5.
  30. Thornton PD, Liese K, Adlam K, et al. Calculators Estimating the Likelihood of Vaginal Birth After Cesarean: Uses and Perceptions. J Midwifery Womens Health 2020;65(5):621-6.
  31. Tulandi T, Agdi M, Zarei A, et al. Adhesion development and morbidity after repeat cesarean delivery. Am J Obstet Gynecol 2009;201(1):56 e1-6.
  32. Turner MJ, Agnew G, Langan H. Uterine rupture and labour after a previous low transverse caesarean section. BJOG 2006;113(6):729-32.
  33. 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.
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