New Insights into VBACs and Maternal and Neonatal Outcomes
New Insights into VBACs and Maternal and Neonatal Outcomes
Abstract & Commentary
By John C. Hobbins, MD, Professor and Chief of Obstetrics, University of Colorado Health Sciences Center, Denver, is Associate Editor for OB/GYN Clinical Alert.
Dr. Hobbins reports no financial relationship to this field of study.
Synopsis: A recent review of the literature shows, and an NIH consensus panel concludes, that a trial of labor, when compared with a repeat cesarean section, is associated with a lower risk of maternal death and morbidity, but with a slightly higher risk of perinatal mortality and uterine rupture.
Sources: Guise JM, et al. Vaginal birth after cesarean. New insights on maternal and neonatal outcomes. Obstet Gynecol 2010;115:1267-1278; National Institutes of Health Consensus Development Conference Statement: Vaginal birth after cesarean: New insights March 8-10, 2010. Obstet Gynecol 2010;115:1279-1295.
Although some aspects of vaginal birth after cesarean delivery (VBAC) have been covered in previous OB/GYN Clinical Alert issues, I cannot pass up an opportunity to comment on two papers appearing in the June issue of Obstetrics & Gynecology. One was a critical review of the literature on a trial of labor (TOL) in patients who had previous cesarean deliveries and the other was a consensus statement from a National Institutes of Health (NIH) Development Conference Panel on VBAC.
Guise et al sifted through data from 203 articles that satisfied their inclusion criteria and attempted to answer questions that would be covered by the NIH consensus panel regarding maternal and neonatal outcomes with VBAC. Using what they construed to be the best studies, they found maternal mortality to be significantly lower (relative risk [RR], 0.33; 95% confidence interval [CI], 0.13-0.99) with TOL than with elective repeat cesarean section (RCS). If they only looked at term pregnancy, the RR was 0.27 (95% CI, 0.09-0.85). Fortunately, the actual risk of a patient dying from either route was low 4/10,000 for TOL and 13/10,000 for elective RCS.
Regarding uterine rupture, the pooled data from the best studies showed an overall rate of uterine rupture to be 0.47% for TOL and 0.03% for elective RCS. The average stay in the hospital for TOL was 2.6 days vs 3.9 days for RCS. Perinatal mortality was higher with TOL than RCS (0.11% vs 0.06%; RR, 2.06; 95% CI, 1.35-3.13). Much of this increased risk was contributed by those needing emergency cesarean section during a TOL. There were no significant differences between TOL and RCS regarding the need for hysterectomy, transfusion, or the rate of perinatal infection. Even with pooled data, there was insufficient information for the authors to comment on neonatal sepsis or neurological outcomes.
In summary, the group found a higher rate of uterine rupture with TOL (< 1/200) and perinatal death (1.3/1000), but less chance of maternal death and fewer days in the hospital.
Commentary
The Guise et al study served as a source of outcome data, along with many other studies, that the NIH panel used in their deliberations and the ultimate report. Here is the backdrop, and undoubtedly the motivation behind the NIH panel's creation. In 1990, the cesarean section rate in the United States was 22.7% and the VBAC rate was 19.9%. At about that time, there was a push to decrease the cesarean section rate to 15% and VBACs were encouraged as a way to avoid repeat cesarean sections. Following this stated goal, the VBAC rate rose to 28.3% during the next 6 years, while the cesarean section rate dropped to 20.7%. However, soon thereafter, VBAC fell victim to the circumstances described below, causing the rate to drop steadily to 8%. Now the cesarean section rate in the United States is 32.8% (2008 data), and, currently, about 1.5 million cesarean sections are done yearly at a cost of $7.8 billion.1
What were the circumstances behind the above trend? In 1999 the American College of Obstetricians and Gynecologists (ACOG) issued practice guidelines that suggested patients be "offered" VBAC, instead of their previous 1990 wording, "encouraged," and the guidelines indicated that centers offering TOL should have a physician capable of doing a cesarean section to be "immediately available" during a patient's labor. Anesthesia guidelines followed the same "immediately available" requisite. At the same time, another VBAC deterrent emerged, as demonstrated by a 2009 ACOG survey showing that 30% of obstetricians stopped doing VBACs because of fear of litigation. Not surprisingly, some hospitals decided to no longer offer this option and many practitioners followed suit.
So, for those women who want a TOL, and who have a provider that supports it and a center that permits it, here is what they can be told about the real risks and benefits of TOL. Based on all available data:
- The chance of a successful vaginal delivery is, on average, 74%, with a 63% chance in patients with no previous vaginal delivery, an 83% chance with a vaginal delivery prior to the previous cesarean section, and a 95% chance in those with a prior VBAC.
- The risk of uterine rupture is about 0.47% overall, but undoubtedly lower in ideal candidates. Rates of rupture are higher with more than one prior cesarean section and in those who are induced, but the data do not support there being a higher rate when oxytocin augmentation is used for spontaneous labor.
- Maternal mortality is lower (RR, 0.37), but perinatal mortality is higher (RR, 2.6). Perinatal death occurs in 6% of uterine ruptures, and in 3% of ruptures at term (overall, representing 2 perinatal deaths per 10,000 TOL).
- Regarding downstream maternal complication of TOL, specifically pelvic floor disorders, the NIH panel concluded that elective cesarean section "should not be considered protective against stress incontinence and prolapse."
- Maternal benefits of TOL would include a 60%-80% chance to avoid a cesarean section and its postoperative complications, and a decrease in the chances of placenta previa and accreta in subsequent pregnancies.
The statement in the report that is most debatable is: "Unfortunately, there is no reliable way to predict who will have a uterine rupture." Uterine wall thickness has been repeatedly shown to correlate with uterine rupture during TOL,2,3 and Bujold et al have correlated uterine scar thickness < 2.3 mm (OR, 4.5), a birth-to-birth interval of < 18 months (OR, 6.7), and single-layer closure (OR, 5.7) with the risk of rupture.4
Therefore, it is likely that patients who fulfill some, but not necessarily all, of the following criteria should expect a low risk of uterine rupture and its consequences.
- A previous VBAC or any vaginal delivery
- More than 18 months between births
- Only one prior cesarean section
- A uterine wall thickness > 2.3 mm
- A double-layer closure
- An estimated fetal weight < 4000 g
- Spontaneous labor
The most difficult variables to deal with are the fears of providers about their legal vulnerability, the continued inability of hospitals to comply with TOL guidelines, and the common misconception among patients that cesarean section will prevent urinary complications and later sexual dysfunction.
References
- Gotoh H, et al. Predicting incomplete uterine rupture with vaginal sonography during the late second trimester in women with prior Cesarean. Obstet Gynecol 2000;95:596-600.
- Rozenberg P, et al. Ultrasonographic measurement of lower uterine segment to assess risk of defects of scarred uterus. Lancet 1996;347:281-284.
- Grobman WA, et al. Prediction of uterine rupture associated with attempted vaginal birth after cesarean delivery. Am J Obstet Gynecol 2008;199:30.e1-5.
- Bujold E, et al. Prediction of complete uterine rupture by sonographic evaluation of the lower uterine segment. Am J Obstet Gynecol 2009;201:320.e1-6.
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