Vaginal birth after Cesarean Section Revisited — 2008
Abstract & Commentary
By John C. Hobbins, MD, Professor and Chief of Obstetrics, University of Colorado Health Sciences Center, Denver
Dr. Hobbins reports no financial relationship to this field of study.
Synopsis: Again, VBACs have been shown to be a safe and successful option, especially in those who have already had a prior VBAC.
Source: Mercer BM, et al. Obstet Gynecol. 2008;111: 285-294.
In a previous Clinical Alert, the risk of uterine rupture in patients attempting vaginal birth after cesarean sections (VBACs) was addressed when it appeared that there was a distinct downturn in the amount of VBACs being done in the USA. This most likely was due to an inability of some practitioners and hospitals to comply with anesthesia and physician availability requirements, as well as medical legal concerns. However, a recent article appeared in Obstetrics and Gynecology which could not be passed over, since it shed more light on which patients would be least likely to have uterine ruptures if they chose to attempt a VBAC.
In a collaborative effort by the NICHD Maternal Fetal Medicine Network, Mercer et al reviewed the records of 13,532 women attempting VBACs in 19 centers from 1999 to 2002. The endpoints evaluated were: 1) the number of successful attempts at vaginal birth, 2) the incidence of through-and-through uterine rupture, 3) the incidence of intrauterine dehiscence (with the serosa intact), and 4) neonatal morbidity. The independent variable was the number of prior VBACs.
In all three of the above categories, there was a large jump in the rate of successful VBACs and a precipitous drop in complications when patients had had at least one prior VBAC. For example, the success rate was 63% for those with no prior VBACs, 87.6% with 1 VBAC, 90.9% with 2 VBACs, 90.6% with 3 VBACs, and 91.9% with 4 or more. The risk of uterine rupture was 0.87%, 0.45%, 0.38%, 0.54%, and 0.52% for each of the above categories, respectively. The incidence of dehiscence dropped from 0.98% with no prior VBACs to 0.24% after one and then leveled out at 0.25% for every category thereafter. Neonatal morbidities were not significantly different between categories, although there was a trend towards decreased incidences of low Apgar scores and neonatal encephalopathy with increasing numbers of prior VBACs. As expected, maternal morbidity was related to the necessity for cesarean section.
The point here is that having had one prior successful VBAC decreased the risk of rupture and dehiscence by 50% to 75%, respectively, after which the risk leveled off with more than one prior VBAC. Also, those having had one or more successful prior VBACs had over a 90% chance of being successful again. Interestingly, even those with no track record ran a 63% chance of delivering vaginally.
Commentary
The latest published figures from the CDC from 2005 show a cesarean section rate in the USA to be 30.2%, with a surprising amount of states exceeding that figure. Almost three quarters of these were primary sections so, unless patients are given a chance to have VBACs, "we ain't seen nothing yet." With the fear of uterine rupture and the misguided idea that cesarean section will neutralize any tendency towards later stress incontinence, many patients are strongly requesting elective cesareans, and their providers are hesitant to stand in their way for a variety of reasons. The problem is that often these patients are unaware of the downside of cesarean section, putting this major (still) operation in the same risk category as a Botox injection.
This paper, encompassing an impressive number of patients, shows that the chance of uterine rupture with VBAC is about 1 in 100 for those without a prior VBAC and about 1 in 400 for those having had one or more prior VBACs. Also, those in the latter category have a 9 in 10 chance of avoiding a cesarean section.
In a previous Clinical Alert, the risk of uterine rupture in patients attempting vaginal birth after cesarean sections (VBACs) was addressed when it appeared that there was a distinct downturn in the amount of VBACs being done in the USA.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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