Volume 4, No. 8, August 2006
Abstract of the Month
Rate of uterine rupture hasn’t changed for 20 years – Why have our practices changed?
The rate of symptomatic uterine rupture has been quoted at 0.5% - 1.0% for the last 20 years. The constant data has been very discordant with the changes in practice that we have seen recently, and the increased concentration / discussion regarding a increasing(sic) risk of rupture.
Luckily, several recent publications add significant information to our understanding of vaginal birth after cesarean (VBAC) and suggest that a reversal of the dramatic move away from VBAC may be in order. Nationally, the number of hospitals offering VBAC services has decreased dramatically over the past several years. Of those facilities that do offer VBAC, some allow a trial of labor for women in spontaneous labor but will not offer augmentation or induction of labor. Also, some hospitals restrict a trial of labor to women with only one prior cesarean delivery, even for those women who have had a previous vaginal birth. As I.H.S. facilities with full scope Ob/Gyn departments have largely continued to offer VBAC services, it is encouraging to see VBAC re-evaluated from a more balanced and evidence-based perspective.
Induction of Labor
This month ACOG issued a new Committee Opinion addressing the safety of induction of labor for patients who have had a prior cesarean delivery. The abstract states:
Induction of labor in women who have had cesarean deliveries may be necessary because of fetal or maternal indications. The potentially increased risk of uterine rupture should be discussed with the patient and documented in the medical record. Selecting women most likely to give birth vaginally and avoiding the sequential use of prostaglandins and oxytocin appear to offer the lowest risks. Misoprostol should not be used in patients who have had cesarean deliveries or major uterine surgery.
This Committee Opinion offers a concise review of recent studies of VBAC and induction of labor and points out that previous studies may have overestimated the risk of uterine rupture with induction. For example, the study by Lydon-Rochelle et al. was a retrospective, population-based study relying on ICD-9 codes for diagnosis of uterine rupture. Lydon-Rochelle reported the following rupture rates: 0.16% for repeat cesarean delivery, 0.52% for spontaneous labor, 0.77% for labor induced without prostaglandins, and 2.4% for labor induced with prostaglandins. The Committee Opinion notes that there was no significant difference in the rates of uterine rupture with spontaneous labor or labor induced without prostaglandins in this study.
More recent literature about induction is also presented. This includes the prospective multi-center observational study by Landon, et al., where the outcomes experienced by 33,699 women with previous cesarean deliveries were analyzed. Chart review confirmed 124 cases of uterine rupture in the 17,898 women undergoing a trial of labor, with the following rates: 0.4% for spontaneous labor, 0.9% for augmentation of labor, and 1% for induction of labor. Additionally, this study reports a risk of rupture of 1.1% with oxytocin alone, 0.9% with mechanical dilation (+ oxytocin), and 1.4% when prostaglandins and oxytocin were used in combination. The odds ratio of rupture, in comparison to the women who labored spontaneously, was 2.42 for augmentation of labor and 2.86 for induction of labor with the highest risk associated with prostaglandins and oxytocin used in combination (O.R. 3.95). Misoprostol was one of the prostaglandins used in this study. Interestingly, there were no cases of rupture in women induced only with prostaglandins, which they suggest is due to these women going into labor “easily”.
The new Committee Opinion also cites another large retrospective study (Macones) of 25,005 women conducted by medical record data abstraction at both tertiary and community hospitals. This study found an overall risk of rupture of 0.98% (0.4% in women who also had a prior vaginal delivery). The odds ratio of uterine rupture was 3 times higher in women who underwent induction or augmentation of labor, in comparison to those who labored spontaneously. However when specific methods were assessed in multivariate analysis, in comparison to spontaneous labor, the odds of uterine rupture was 1.61 with augmented labor, 0.85 induced without oxytocin or prostaglandin, 1.46 with oxytocin alone, 1.90 with prostaglandin alone, and 4.54 with oxytocin and prostaglandins used in combination. Only the increased odds of rupture associated with combined oxytocin and prostaglandin use was statistically significant. Misoprostol was not used in this study population.
Based on this information, the Committee Opinion concludes:
Induction of labor remains a reasonable option, but the potentially increased risk of uterine rupture associated with any induction should be discussed with the patient and documented in the medical record. Selecting women most likely to give birth vaginally and avoiding sequential use of prostaglandins and oxytocin appear to offer the lowest risks of uterine rupture. Misoprostol should not be used in patients who have had cesarean deliveries or major uterine surgery.
This committee opinion is firm in its recommendation to avoid the use of Misoprostol but supports the use of oxytocin augmentation and induction in selected patients with appropriate counseling and does not mandate the avoidance of all prostaglandins. As the most recent (2004) ACOG Practice Bulletin on VBAC cautions against the use of any prostaglandins in women undergoing a trial of labor, widespread use of prostaglandins is not likely without further clarification from ACOG. Nonetheless, this additional information about the risks associated with augmentation and induction of labor will be helpful in counseling patients and the data suggests that the overall increase in risk associated with augmentation and induction of labor is less than previously stated.
Two Prior Cesarean Deliveries
The two recent large studies of VBAC also offer new data about the advisability of VBAC for woman with two prior cesarean deliveries who desire a trial of labor. ACOG addressed this situation briefly but emphatically in the 2004 Practice Bulletin. That recommendation was based primarily on a study by Caughey et al. which was a retrospective chart review of all patients undergoing a trial of labor at a single facility over a twelve year period. The 3757 women with a single prior scar experienced a rupture rate of 0.8% while 3.7% of women with two prior scars experienced uterine rupture (5 of 134). They note that the risk of uterine rupture was nearly 5 times greater for women with two previous scars compared to one scar. In a multivariate regression analysis they also note that the risk was of rupture with 2 scars was only one-fourth as great if the woman had also had a prior vaginal delivery. ACOG concluded that for women with 2 prior cesarean deliveries, only those with a prior vaginal delivery should be considered candidates for a trial of labor.
Macones et al. have reviewed their retrospective data from both tertiary and community hospitals which included 20,175 women with one previous cesarean delivery and 3,970 women with two previous cesarean deliveries. The rates of successful VBAC were similar (75.5% and 74.6% respectively). The risk of rupture was lower for women with one prior cesarean delivery (0.9% vs. 1.8% for the women with two prior cesarean deliveries). The history of a prior vaginal birth was associated with a lower risk of rupture (0.5% vs. 2.4% with no prior vaginal delivery history). The odds ratio of major morbidity was 2.26 for women with 2 prior cesarean deliveries who elected a trial of labor compared to a repeat cesarean delivery. As the absolute risk of major morbidity remains small, these investigators conclude that a VBAC attempt remains a reasonable option for women with 2 prior cesarean deliveries.
Landon et al. have also analyzed the data from their study to address this issue. Their prospective observational study found rates of uterine rupture of 0.7% (115 of 16,915 women with a single prior cesarean delivery) vs. 0.9% (9 of 975 women with a history of more than one prior cesarean delivery) for women undergoing a trial of labor. The VBAC success rate was 74% for those with one prior scar and 67% with two prior scars. (The study also included 84 women with 3 prior scars and 20 women with 4 prior scars; these women experienced a 63% and 55% success rate respectively.) The difference in the absolute rates of uterine rupture for the subset of women with multiple prior scars who had experienced a previous vaginal delivery (1%) and who had not had a previous vaginal delivery (0.85%) was not statistically significant. Prior vaginal delivery was protective in the overall analysis with an odds ratio of uterine rupture of 0.5 compared to those women who had not given birth vaginally in the past. The odds of major maternal morbidity associated with a trial of labor for women with multiple prior cesarean deliveries was 1.41.
Both studies demonstrate that the absolute risk of uterine rupture for women with a history of two prior cesarean deliveries is small. This information suggests that, with appropriate counseling and labor management, women with two prior cesarean deliveries and are otherwise acceptable VBAC candidates may be allowed to proceed with a trial of labor. An absolute requirement for a prior vaginal delivery is not supported by these findings, although prior vaginal delivery is an additional predictor for success.
Resources for VBAC
All Navajo Area facilities with full-scope Ob/Gyn services continue to offer VBAC, as do a number of other I.H.S. sites. For more information about strategies to optimize safety for women undergoing a trial of labor, the work of the Northern New England Perinatal Quality Improvement Network remains an excellent reference. NNEPQIN has put forth guidelines for risk stratification and resource development on their web site. These guidelines classify as low risk women with one prior uterine scar presenting with spontaneous labor and without FHR abnormalities. Medium risk women are those undergoing induction or augmentation, with 2 or more previous scars, or with a <18 month inter-delivery interval. High risk women are defined as those with repetitive non-reassuring FHR abnormalities, bleeding suggestive of abruption, or 2 hours without cervical change in active labor despite adequate contractions. They then describe appropriate resources needed to manage each risk group. The NNEPQIN site also has model consent forms and patient information as well as suggestions about conducting drills. Dr. Lauria, one of the leaders of the ACOG-award winning NNEPQIN VBAC project, will be returning to speak at the triennial I.H.S. Ob/Gyn meeting in Albuquerque in August 2007.
From Jean Howe, Chinle
OB/GYN CCC Editorial comment:
The VBAC pendulum is beginning to swing back toward a more reasonable approach
Clearly the national benchmark recommendations that women with 2 previous cesarean deliveries and no vaginal delivery should have a repeat cesarean delivery should be reexamined in light of this new information.
Likewise, cervical ripening and induction of labor with oxytocin and foley bulbs can be considered as the data suggests that the overall increase in risk associated with augmentation and induction of labor is less than previously stated.
In addition, as we counsel our patients we should not just speak in terms of odds ratios or relative risks, but in terms of attributable risk or marginal risks - above the baseline risk. For instance, the Network data in the Landon study demonstrated that the rate of hypoxic ischemic encephalopathy was actually quite small at approximately 1 / 2,000 trials of labor.
I encourage you to take advantage of unique opportunity available to staff who provide care for Indian Health women and children. One of the foremost experts on this issue and how implement reality obstetric based drills, Dr. Lauria, will be one of the Key Note Speakers at the next National Women’s Health and MCH Meeting August 15-17, 2007. There will also be presentations on successful implementation of emergency obstetric drills from the staff of Phoenix Indian Medical Center.
Special thanks to Jean Howe from Chinle for this month’s Abstract(s) of the Month.
Resources
ACOG, Induction of Labor for Vaginal Birth after Cesarean Delivery, ACOG Committee Opinion #342, August 2006.
Lydon-Rochelle M, et al. Risk of uterine rupture during labor among women with a prior cesarean delivery. N Engl J Med 2001;345:3-8.http://content.nejm.org/cgi/reprint/345/1/3.pdf
Landon MB , et al. Maternal and perinatal outcomes associated with a trial of labor after prior cesarean delivery. N Engl J Med 2004;351:2581-9. http://content.nejm.org/cgi/reprint/351/25/2581.pdf
Macones GA, et al Maternal complications with vaginal birth after cesarean delivery: a multicenter study. Am J Obstet Gynecol. 2005;193:1656-62.
ACOG, Vaginal Birth after Previous Cesarean Delivery, ACOG Practice Bulletin #54, July 2004. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=
pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=15229039
Caughey AB, et al Rate of uterine rupture during a trial of labor in women with one or two prior cesarean deliveries. Am J Obstet Gynecol. 1999;181:872-6.
Macones GA, et al. Obstetric outcomes in women with two prior cesarean deliveries: is vaginal birth after cesarean delivery a viable option? Am J Obstet Gynecol. 2005;192:1223-9.
Landon, et al. Risk of uterine rupture with a trial of labor in women with multiple and single prior cesarean delivery. Obstet Gynecol 2006;108:12-20. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db
=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=16816050
Northern New England Perinatal Quality Improvement Network
http://www.nnepqin.org/nneob/servlet/ViewPage?id=3
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OB/GYN
Dr. Neil Murphy is the Obstetrics and Gynecology Chief Clinical Consultant (OB/GYN C.C.C.). Dr. Murphy is very interested in establishing a dialogue and/or networking with anyone involved in women's health or maternal child health, especially as it applies to Native or indigenous peoples around the world. Please don't hesitate to contact him by e-mail or phone at 907-729-3154.
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