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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