by Henci Goer

Commentary on: Lieberman, E., Ernst, E. K., Rooks, J. P., Stapleton, S., & Flamm, B. (2004). Results of the national study of vaginal birth after cesarean in birth centers. Obstet Gynecol, 104(5 Pt 1), 933-942. [Abstract]

Study design and results: multicenter prospective study of 1,453 women with prior cesarean who presented in labor at 52 U.S. free-standing birth centers. Study concluded that birth centers should refer women desiring VBAC to hospitals on grounds that they are more likely to experience labor complications.

VBAC rate: 87% overall, 94.4% of women with prior vaginal birth and 80.9% of women with no prior vaginal birth. Fifty-four percent of women had no prior vaginal births.

Transfer to hospital:

• intrapartum: 347 women (24%) transferred during labor
• immediate transfer for complications noted at arrival at birth center: 23 women
• emergency transfer rate: 2.6% of women were transferred emergently in labor. This represented11% of all transfers (37 / 347). In 30 cases the time from decision to hospital arrival was known. The range was 3-60 min, and 90% arrived within 25 min. In 15 cases the time from arrival to treatment was known. Nine of these women had cesareans. The time from decision to transfer to cesarean ranged from 24-120 min, median 35 min.
• transfer rate in women with prior vaginal birth was 11% vs 35% in women with no prior vaginal birth.
• postpartum: An additional 42 women and babies (3.8%) transferred after birth, 22 for maternal and 20 for neonatal reasons.

Complications:

• uterine rupture: 6 (4 per 1,000) overall; 3 (2 per 1,000) in women with 1 prior cesarean, 3 (30 per 1,000) in women with more than 1 prior cesarean.
• hysterectomy: 1 (less than 1 per 1,000)
• Intrapartum or neonatal death: 7 (5 per 1,000) of which 2 were associated with uterine rupture.
• Perinatal deaths in infants of women defined as low risk (less than or equal to 42 wks gestation, 1 prior c/sec): 3 (2 per 1,000), none associated with uterine rupture.

Comparison with other studies comparing VBAC and planned repeat cesarean: Investigators compared birth center outcomes with studies in which the participating institutions met current American College of Obstetricians and Gynecologists recommendations that obstetricians and anesthesiologists be immediately available. Despite higher uterine rupture rates and populations that were at somewhat higher risk than birth center clients, perinatal mortality rates were lower in these institutions.

Problems: This study ‘s flaw lies neither with how it was carried out nor with how the investigators reported it, but rather with its conclusion, a discussion deferred to the “Comment” section below. First, however, three points merit consideration:

• Birth center midwives achieved substantially higher VBAC rates in women with no prior vaginal births: Hospital-based VBAC studies don’t seem able to achieve higher VBAC rates than 70-75% even when including women with prior vaginal births, a factor that boosts VBAC odds over 90%.(3, 6) In this study, 81% of women with no prior vaginal births had VBACs. This means that 6 additional women or more in every 100 with no prior vaginal birth would give birth vaginally if they chose a birth center, effectively ending their exposure to the risks of repeat surgery.
• Birth center midwives achieved substantially lower uterine rupture rates than typical of U.S. studies: In this study, 4 women per 1,000 overall experienced uterine rupture, falling to 2 women per 1,000 with no more than 1 prior cesarean. This low rate is almost certainly because birth centers do not induce labor or use oxytocin to augment labor. For example, Landon et al. also reported a 4 per 1,000 uterine rupture rate in women laboring spontaneously, but with induction or augmentation, uterine rupture rates rose to 10 and 9 per 1,000, respectively. (3) This means that 5 additional women or more in every 1,000 might avoid uterine rupture and the dangers that accompany it by choosing a birth center.
• This study further reinforces that cesarean surgery compromises the health and well-being of babies of future pregnancies even when nothing seems amiss: The mortality rate during labor and in the neonatal period was 5 per 1,000 versus 0.6 per 1,000 in an earlier study of nearly 12,000 women admitted in labor to U.S. birth centers. (5) Here, as in Landon et al., we see that seemingly healthy babies of low-risk women who are not first-time mothers experience higher rates of death and hypoxic injury despite intact uterine scars. Independently of the scar giving way, babies developing in a cesarean-scarred womb may be less able to tolerate the normal stress of labor, much less the extra stress of induction or augmentation. No one in the mainstream debate surrounding cesarean surgery—and especially not those promoting elective primary cesarean—have considered this disturbing aspect of cesarean section.

Comment: The study concludes that all planned VBACs should take place in the hospital. Susan Hodges, Director of Citizens for Midwifery, criticizes this conclusion, pointing out that: (1, 2)

• The investigators did not demonstrate that the differential in perinatal outcomes between birth centers and hospitals was statistically significant (unlikely to be due to chance): In point of fact, 3 of the 7 deaths (true knot in the cord presenting as bradycardia on arrival, shoulder dystocia, breech with prolapsed cord on arrival) in particular seem equally likely to have occurred in women with unscarred uteruses planning hospital birth.
• When assessing the “safety” of VBAC, the investigators focused on perinatal mortality to the exclusion of other short- and long-term hazards of cesarean section: As we saw above, choosing birth center VBAC protected against both repeat cesarean and uterine rupture and thereby the dangers that accompany them.
• Focusing on perinatal outcomes assumes that any risk to the baby supersedes any risk to the mother: “This,” Hodges writes, “is a value judgment neither supported by the data nor legally valid.” (2, p. 898)
• Recommending universal hospital birth assumes that all women with prior cesareans would be better off by doing so: Implicit in this assumption is that women have ready access to care providers and hospitals supportive of VBAC. This is manifestly not the case. In whole regions of the country, VBAC has become impossible to obtain even for women with prior VBACs. In other cases there are so many unreasonable restrictions unsupported by the research that VBAC remains inaccessible to most women who desire this option. This recommendation also assumes that all VBAC candidates are alike, though women with no more than one prior cesarean who did not exceed 42 weeks gestation were much less likely to experience adverse outcomes.

The heart of the matter is this: As Hodges writes, the recommendation to confine VBAC to hospitals “makes a mockery of ‘informed consent’ and ‘informed refusal’ . . . [and] condemns the majority of mothers with prior cesareans to repeat cesareans, most of which are unnecessary.” (2, p. 898)

Bibliography:

1. Hodges, S. (2004). Personal communication.
2. Hodges, S. (2005). Results of the national study of vaginal birth after cesarean in birth centers [Letter]. Obstetrics & Gynecology, 105(4), 897.
3. Landon, M. B., Hauth, J. C., Leveno, K. J., Spong, C. Y., Leindecker, S., Varner, M. W., et al. (2004). Maternal and perinatal outcomes associated with a trial of labor after prior cesarean delivery. N Engl J Med, 351(25), 2581-2589.
4. Maternity Center Association. (2004). Effects of cesarean and vaginal birth on mothers, babies, and future reproductive capacity: A rapid systematic review. from http://www.childbirthconnection.org/article.asp?ck=10271&ClickedLink=200&area=2
5. Rooks, J. P., Weatherby, N. L., Ernst, E. K., Stapleton, S., Rosen, D., & Rosenfield, A. (1989). Outcomes of care in birth centers. The national birth center study. N Engl J Med, 321(26), 1804-1811.
6. Smith, G. C., Pell, J. P., Cameron, A. D., & Dobbie, R. (2002). Risk of perinatal death associated with labor after previous cesarean delivery in uncomplicated term pregnancies. JAMA, 287(20), 2684-2690.