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VBAC Cubby - vaginal birth after cesarean

Summary of the Four Largest and Most Recent VBAC and Elective Repeat Cesarean Studies
by Gretchen Humphries
The purpose of this article is to provide a simple summary of the four largest and most recent studies done on vaginal birth after cesarean (VBAC) and elective repeat cesarean (ERC). Because complications associated with any form of birth are rare events, large numbers of births must be studied to gain an accurate measure of those complications. It is important to not rely on interpretation of opinion when making a decision about VBAC, but rather to assess the available data and make an informed decision based on fact, not emotion. While I have very strong opinions about the inherent flaws, and even dangers represented by the medical model of obstetrical care, the fact is that most women plan births within that system. Therefore, it is appropriate to look at the information provided by that system.

There are serious flaws in all of these studies; flaws that may over-estimate the risks specifically associated with VBAC. Nevertheless, the results of these studies still support VBAC as a safe and reasonable choice for most women. Uterine rupture is the one obstetrical complication that is most popularly associated with VBAC trials of labor (TOL) and as such, is often used to discourage VBAC TOLs, in spite of its rarity. While these studies do not accurately assess the risk of uterine rupture in a completely unmedicated VBAC (there are no published studies that do so), they probably do accurately assess the risk involved in a typical hospital VBAC as managed by an obstetrician.

Study 1

"Risk of Uterine Rupture During Labor Among Women With a Prior Cesarean Delivery" Lyndon-Rochelle M, Holt VL, Easterling TR, Martin DP NEJM Vol. 345, 3-8 July 5, 2001.

20,095 women with 1 prior cesarean section comprised the study group. They each gave birth to a live, single infant between 1987 and 1996.

Uterine rupture:

Elective repeat cesarean (ERC) with no labor: 0.16% (11 of 6980)
Spontaneous onset of Labor (SOOL): 0.52% (56 of 10,789)
Induction of Labor without Prostaglandin: 0.77% (15 of 1960)
Induction of Labor with Prostaglandin: 2.45% (9 of 366)
The overall risk of uterine rupture in all TOL groups was 0.6% (80 of 13115)
There was no information given about augmentation of labor in any of the groups that labored.

Complications such as diabetes mellitus, chronic hypertension, pre-eclampsia, breech presentation, genital herpes or placenta previa were not associated with a higher risk of uterine rupture. Likewise, prior lower vertical incision was not associated with an increased risk of uterine rupture.

Fetal Deaths:

There were 5 fetal deaths in the women that had uterine ruptures (91 total ruptures). The authors didn't report which specific groups were involved. There were 100 fetal deaths in the women that did not have uterine ruptures (20,004 total).

If all of the uterine rupture associated deaths occurred in the groups of women that labored, then the risk of the baby dying as a result of a uterine rupture associated with TOL is 0.04% (5 of 13115), over 10 times less than the risk of the baby dying for any other reason (0.5% or 100 of 20,004).

Conclusion from the study:
"At present, the data suggest that induction of labor increases the risk of uterine rupture among women with one prior cesarean delivery and that labor induced with use of a prostaglandin confers a greater relative risk. The overall effect of induction of labor with prostaglandins on uterine rupture is still unclear and may vary according to the preparation used, the regimen, and the degree of cervical readiness for induction."

Study 2

"Elective repeat cesarean delivery versus trial of labor: A meta-analysis of the literature from 1989 to 1999" Mozerkewich, EL and Hutton EK. Am J Obstet Gynecol Vol. 183, 1187-1197, Nov. 2000

The authors of this study searched MEDLINE and EMBASE databases for all English language published reports, between 1989 and 1999, on VBAC, TOL, trial of scar (TOS) and uterine rupture. They selected a total of 15 studies that were of a quality and make-up to be appropriate for meta-analysis - they pooled the data from each individual study together and re-analysed the data as a whole, as appropriate for each item they were analyzing.

They analyzed for uterine rupture, maternal mortality, fetal or neonatal mortality, low APGAR score, maternal transfusion and hysterectomy. Uterine rupture was defined as symptomatic, requiring surgical repair or involving extrusion of fetal parts. All women who chose ERC were eligible for a TOL and opted for surgery instead.

28,813 women attempted VBAC with 20,746 achieving a vaginal birth (72.3%).

Uterine Rupture:

TOL group: uterine rupture rate was 0.4% (4 of 1000)
ERC group: uterine rupture rate of 0.2% (2 of 1000)

Maternal Deaths and Complications:
There were 3 maternal deaths among 27,504 women in the TOL group. All 3 women were undergoing a repeat cesarean after TOL. There were no maternal deaths among 17,740 women undergoing an ERC. The difference between the 2 groups was not statistically significant.

Maternal febrile morbidity (fever) was less frequent among women in the TOL group. This was significant across all the studies that looked at this complication.

Need for a transfusion was significantly less among women in the TOL group. This was significant across all the studies that looked at this complication.

Need for a hysterectomy was significantly less in the TOL group in all but 1 study, which found no difference between TOL and ERC groups.

Fetal Deaths and Complications:

Deaths due to intrauterine death before labor, lethal birth defects and prematurity were excluded.

TOL births: 0.2% (38 of 19,842).
ERC births: 0.1% (10 of 13,292).
There was no way to determine the actual cause of any of these deaths, so no conclusions can be drawn as to the impact uterine rupture may or may not have had, as opposed to other obstetrical conditions and interventions.

5-minute APGAR: 7 was more common in the TOL group but this was statistically significant in only 2 of 7 studies that were used for this comparison.

Facts of note:

Between 693 and 3332 women would need to undergo ERC to prevent a single fetal or neonatal death attributable to TOL.
Between 374 and 809 women would need to undergo ERC to prevent a single case of uterine rupture.

Conclusion from the study:
"Our findings suggest that small increases in the uterine rupture rate and in fetal and neonatal mortality rates may result from a trial of labor with respect to elective repeat cesarean delivery. These increases may be counterbalanced by reductions in maternal morbidity with a trial of labor, including febrile morbidity, transfusion, and hysterectomy. Either a trial of labor or elective repeat cesarean delivery may be a reasonable option for women with at least one previous cesarean delivery."

Study 3

"Vaginal Birth After Cesarean and Uterine Rupture Rates in California" Gregory KD, Korst, LM, Cane P, Platt, LD, Kahn, K. Obstet & Gynecol Vol.94, 985-989, Dec. 1999

This study looked at the hospital discharge data for 536,785 women who gave birth in California in the year 1995.

The overall cesarean rate that year was 20.8% (111,374 of 536,785)
Women who had previous cesarean(s) were 12.5% (66,856 of 536,785) of the study group.
ERC: 40.3% (26,943 of 66,856)
TOL: 59.7% (39,913 of 66,856).
Successful VBAC: 61.4% (24,024 of 66,856)
VBAC in all women with previous cesarean: 35.9%
A hospital that had at least a 60% TOL rate in women with previous cesarean was defined as having a "high attempted VBAC rate". Women who gave birth in a high VBAC rate hospital (286,007 - includes women that did not have a previous cesarean) had lower cesarean rates (18.5%), higher VBAC rates (65.0%) and higher rupture rates (0.088%).
Women that gave birth in a low rate hospital (248,930) had higher cesarean rates (23.3%), lower VBAC rates (55.6%) and lower uterine rupture rates (0.056%).

Uterine Rupture:
The study design did not allow for objective definition of "uterine rupture".

All deliveries: uterine rupture rate was 0.07% (392 of 536,785)
All women with prior cesarean: uterine rupture rate was 0.43% (288 of 66,856)
ERC: uterine rupture rate was 0.28% (79 of 22,760)
TOL: uterine rupture rate was 0.53% (209 of 39,096)
Failed TOL: uterine rupture rate was 1.15% (174 of 15,072)
VBAC: uterine rupture rate was 0.15% (35 of 24,024)
Uterine rupture was 1.9 times more likely if TOL was attempted but only 34% of the uterine ruptures in women with a history of cesarean could be attributed to TOL.

Maternal age was found to be a significant predictor of uterine rupture but the authors were not able to associate this with useful data such as number of prior cesareans or number of previous pregnancies to determine if age was independently important or not.

The data did not include any information on fetal outcome so there was no way to estimate the risk of injury due to uterine rupture.

Conclusion from the study:
".in this ethnically diverse, population-based study, the uterine rupture rate for women attempting a trial of labor was 0.53%. This corroborates the relative safety of VBAC, with respect to uterine rupture, that has been demonstrated in smaller, institutionally-based samples."

Study 4 "Delivery After Previous Cesarean: A Risk Evaluation" Rageth JC, Juzi C, Grossenbacher, H. Obstet and Gynecol 93: 332-337, March, 1999.

The data was collected from questionnaires that were used to collect information for quality-control purposes, in 40% of the deliveries in Switzerland, from 1983 through 1996. All participants in the study had at least one previous birth to the birth recorded in this data set.

Women with a previous cesarean: 11.37% (29,046 out of 255,453).
TOL: 60.64% (17,613 of 29,046).
ERC: 39.36% (11,433 of 29,046).

Spontaneous onset of labor: 86.04% (15,154 of 17,613)
SOOL vaginal births: 75.06% (11,374 out of 15,154)
Induction TOL: 13.9% (2459 out of 17,613)
Induction vaginal births: 65.56% (1612 out of 2459)

Uterine Rupture:

ERC: uterine rupture rate was 0.19%. (22 out of 11,433)
TOL: uterine rupture rate was 0.39% (70 out of 17,613)
Induced TOL: uterine rupture rate was 0.65%
This difference was found to be statistically significant.

41.43% (29 of 70) of the TOL uterine ruptures were augmented labors.
35.80% of the TOL with no ruptures were augmented.
This difference was not found to be statistically significant.

Maternal Complications:

Women in the TOL group were statistically significantly less likely to need a hysterectomy than women in the ERC group (0.16% vs. 0.45%)
Women in the TOL group were statistically significantly less likely to suffer from fever (1.5% vs. 2.29%)
Women in the TOL group were statistically significantly less likely to have thromboembolic complications (0.22% vs. 0.43%)

Women with a prior cesarean were 1.87 times more likely to have a placental abruption during pregnancy and 1.49 times more likely during labor.

Fetal Deaths and Complications:

43 total fetal deaths (not associated with prematurity or birth defects).
ERC: 0.09% (10 of 11,433 or 0.09%)
TOL: 0.19% (33 of 17,613) This difference was slightly statistically significant.

TOL: risk of baby dying due to rupture was 0.03% (5 of 17,613)
ERC: risk of baby dying due to rupture is 0.009% (1of 11,433)

VBAC: babies transferred for further medical treatment was 5.08%.
Unsuccessful TOL: babies transferred for further medical treatment was 8.97%.
ERC: babies transferred for further medical treatment 8.30%.

Other findings:

Epidural anesthesia was associated with a higher risk of rupture but this might be associated with higher epidural use during induction, or other known risk factors.

Cephalopelvic disproportion (CPD) and macrosomia were not associated with higher rates of uterine rupture.

Conclusion from the Study:
"Our data show that a trial of labor after previous cesarean is safe and can be recommended in the majority of cases."

Closing Comments:

All of the studies were based on data collected off of summary paperwork (insurance billing, birth certificates, survey forms, other published studies), completed by many different individuals. Other studies have shown that the error rate in how particular medical events (such as uterine rupture or maternal hemorrhage) are recorded is quite high in this type of analysis. Unless the study authors review the actual medical chart of each individual patient, there is the very real probability that the data used in the study is inaccurate.

Only one of these studies (number 4) made any attempt to determine if augmentation of labor had an effect on rupture rates. While they concluded that it did not, the method they used to draw that conclusion may not have had the statistical power to show significance.

Only one study (number 1) looked at only women with a history of 1 prior cesarean birth and no other births. Multiple cesareans and previous vaginal births are known to have an affect on a number of complications (e.g. uterine rupture rate, placenta previa rates).

There was no information available in any of the studies about specific characteristics of women in the induced labor groups - cervical readiness (Bishop's score) may be an important factor.

Only one study looked at epidural use (study 4) and concluded it was a risk factor for uterine rupture, but not one that could be proven to be independent of other risk factors. There was no analysis of the use of other drugs during labor, nor was there any analysis of how the women labored (for example, confined to bed with electronic fetal monitoring or with artificial rupture of membranes early in the course of the labor).

The fear that is most often played upon when a woman is being "informed" about the risks of VBAC is the death of her baby due to uterine rupture. It is obvious from all of these studies that the risk of this particular outcome is very low in the TOL groups. It is also obvious that ERC is not a guarantee that a rupture will not occur, nor is it a guarantee that a baby will not die. Hopefully this information will put all of the risks associated with VBAC vs. ERC in some perspective.

Once again, it bears mentioning that there are no published studies looking specifically at complication rates in completely unmedicated, "natural" VBACs vs. ERC or a medically managed VBAC. There are certainly no published studies looking at complication rates in out of hospital VBACs. Many people assume that complication rates in the "natural" VBAC would be lower than in any other birth - the fact that induction is a factor in uterine rupture and that epidural use might be, is at least supportive of this assumption. Until data on out of hospital VBACs is published, this must remain an assumption. Hopefully, such a study will be published in the near future.

Copyright © 2002 by Gretchen Humphries. All rights reserved. Used with permission.

Gretchen Humphries is the mother of twin boys, delivered via cesarean section in June, 1998 and of a daughter, born at home in January of 2001. She's also a part-time Doctor of Veterinary Medicine. Her own birth experiences have impassioned her to help other women find and have the births that they want and need.

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