Is Elective Repeat Cesarean Surgery Truly Safer Than Planned VBAC?

The headline on a recent BBC News health article reads: 'Planned repeat C-sections 'safer.' The article goes on to report on two studies that appear to support that conclusion, but do they really? Let's see what the article says and follow with a look at the actual studies.

One of the studies, the BBC News article tells us, is a U.K. study of 159 cases of uterine rupture in which 139 occurred in women with a prior cesarean. The risk of scar rupture in women with a prior scar, it reports, was seven times greater in women having VBAC labors compared with women planning repeat cesareans, and the risk of the baby dying was three times higher.

That would seem to make a clear case for elective (no medical indication) repeat cesarean (ERC), but if we turn to the study itself, we find that the risk of scar rupture in a VBAC labor was 2 per 1000 VBAC labors versus 0.3 per 1000 planned repeat cesareans, or roughly 2 more scar ruptures per 1000 VBAC labors, not the large difference that 'seven times greater' suggests. Moreover, the likelihood of scar rupture was influenced by modifiable factors. The use of prostaglandin, oxytocin, or both for initiating or augmenting labor increased the risk without improving the VBAC rate. In fact, misoprostol was the induction agent in 18% of induced women experiencing scar rupture, but none of the women not having scar rupture were given this agent. ACOG's 2006 induction guidelines for VBAC labors prohibits using misoprostol because of its strong association with scar rupture. Furthermore, study authors theorize that one reason the scar rupture rate was so low in their study compared with some others was because double-layer uterine suturing, another modifiable practice, is the norm in the U.K..

As for VBAC labor tripling the rate of perinatal (intrapartum + neonatal) death compared with ERC, the study doesn't give us this number (or maternal morbidity or mortality rates either, for that matter). The study actually only reports maternal and perinatal outcomes in the population overall, which included 20 women with rupture of an unscarred uterus, an event that may be more likely to produce severe adverse outcomes than a scar rupture. In addition, some of the neonatal deaths in women with prior cesarean may have been in women having emergent nonlabor cesareans. For example, three women had a scar rupture in conjunction with placenta previa. The extensive NIH systematic review of VBAC reported that 6% of babies died as a result of scar rupture in a VBAC labor. We can use that number to calculate the odds of a baby dying in a VBAC labor in the U.K. study by multiplying it (0.06) by the U.K. study's scar rupture rate (0.002). The result equals 0.00012 or 1 perinatal death per 10,000 VBAC labors. To be sure, every death is a tragedy, but we must also put this into perspective: that mortality is equivalent to the maternal mortality rate with ERC, which is 3 per 10,000, and much less than the fetal loss rate as a result of having an amniocentesis, which one modern-day study found to be 60 per 10,000.

The other study, according to the BBC News article, is an Australian study of more than 2000 women planning their second delivery after a first cesarean. The BBC article states that the planned VBAC group had more stillbirths, and women were more likely to have severe bleeding, but gives no numbers.

Again, let's turn to the actual study. The two planned VBAC deaths were unexplained fetal demises in infants born at 39 weeks, the implication being that ERC before that gestational age would have averted them. Perhaps they would have, but as the study I analyzed in another blog post found, ERC at 39 weeks would have prevented only two of the six antepartum deaths.

The excess in severe hemorrhage (defined as > 1500 ml or transfusion) amounted to 1.5 more instances per 1000 VBAC labors, again, a small absolute difference, and a difference, moreover, that probably would have favored planned VBAC had not so few women had vaginal births. Maternal morbidity mostly occurs in labors that end in intrapartum cesareans, and the VBAC rate in this study was a dismal 43%. With physiologic care, the rate could have been as high as 81%. Even with typical management, studies have reported rates ranging from 61-72% in women with no prior vaginal births. In any case, however worrisome at the time, no differences were found in permanent sequelae such as hysterectomy.

And there is more: neither these studies nor the BBC news article considers the downstream consequences of accumulating cesarean scars, but they should. Even women who plan no more children may change their minds or continue with an unplanned pregnancy. According to the NIH systematic review, as the number of cesareans rises so does the risk of serious neonatal and maternal morbidity and perinatal mortality. By contrast, once a woman has a VBAC under her belt, so to speak, she is almost certain to go on having uneventful VBACs. Also, the review found that the risk of forming dense adhesions (internal scar tissue) rises with number of cesareans as well, thus increasing the likelihood of chronic pain and making any future abdominal surgery, not just future cesareans, more risky and difficult. Add these considerations into the mix, and the balance tips toward planning VBAC as the safer option for almost all women.

Headlines and articles like the one from the BBC News obstruct informed decision making by obscuring the true degree of comparative risk, and the studies contribute by failing to emphasize that better labor management in the previous delivery and current labor would improve outcomes. Planned VBAC is not without risks, but neither is ERC. Women deserve accurate, complete, and, most importantly, quantified information on which to decide on mode of birth after a cesarean. They also should have care in the primary cesarean that promotes safety in future VBACs and care in VBAC labors that promotes safe, healthy vaginal birth. To do less than that does women and their babies a serious disservice.

Published: March 28, 2012

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