VBAC Declines but Outcomes Do Not Improve
By Judith Groch, MedPage Today Staff Writer
Reviewed by Zalman S. Agus, MD; Emeritus Professor at the University of
Pennsylvania School of Medicine.
May 30, 2006
Review
FRESNO, Calif., May 30 ¡ª Neonatal and maternal mortality rates did not
improve despite an increase in repeat cesarean deliveries, apparently
engendered by revised guidelines from the American College of Obstetricians
and Gynecologists, researchers here reported.
In 1999, responding to safety and medicolegal considerations, the ACOG
adopted more restrictive guidelines for vaginal birth after cesarean
delivery (VBAC). As a result, attempted VBAC rates declined from 24% to
13.5% in 2002 (P <.001), according to a report in the May/June Annals of
Family Medicine.
The revised guidelines stated that "because uterine rupture may be
catastrophic, VBAC should be attempted in institutions equipped to respond
to emergencies with physicians immediately available to provide emergency
care."
The VBAC decline, however, seems to have continued a trend that began in
1997 and mirrored national trends, perhaps "reflecting unease among
obstetrician and foreshadowing the 1999 revisions, wrote John Zweifler,
M.D., and colleagues at the University of California San Francisco.
Using the California Birth Statistical Master files from 1996 through 2002,
the researchers identified 386,232 California residents who had previously
had a cesarean delivery and had a singleton birth planned in a California
hospital.
The findings were:
Neonatal mortality rates per 1,000 live births for attempted VBAC deliveries
were no different than repeat cesarean delivery rates among neonates
weighing ¡Ý 1,500 g in study period, 1996 to 1999 or 2000 to 2002.
Findings for the two procedures among infants of very low birth weight
differed. Neonatal mortality rates for attempted VBAC deliveries were higher
than those for repeat cesarean deliveries among neonates weighing <1,500 g
in the same periods (attempted VBAC: 1996-1999, 253.2, 95% CI 197.7-308.6;
2000-2002, 336.8, CI, 254.3-419.4; repeat cesarean delivery: 1996-1999,
59.1, CI, 48.3-69.9; 2000-2002, 60.5, CI, 48.4-72.5).
Among all births, multiple logistic regression analysis showed the strongest
predictor of neonatal death to be very low birth weight.
Maternal death rates per 100,000 live births for attempted VBAC deliveries
were similar for both periods (1996-1999, 2.0; CI, 0.1-11.0; 2000-2002, 8.5;
CI, 1.0-30.6).
Overall, recorded pregnancy complications were higher in women who attempted
VBAC than in the cesarean groups in both pre- and post- revision periods,
the researchers said. The rate of attempted VBAC was positively associated
with educational level.
Among the study's limitations, the researchers pointed out that a much
larger sample would be needed to have the power to detect differences in
maternal mortality. The proportion of older women and black women who
attempted VBAC delivery did not decrease after the 1999 revision to the same
extent that it did for younger women or those from other racial and ethnic
groups, a finding consistent with national trends, the researchers said.
The analysis of birth certificate information did not permit the researchers
to assess important neonatal or maternal comorbidities. Other coding
problems and possible misclassifications may also have occurred, they said.
Finally, the researchers wrote, it may be difficult to generalize these
findings to populations outside California, because California births may
occur in settings more or less ethnically diverse or rural compared with
other states. The successful VBAC rate for California women was 8.0%
compared with the national rate of 12.6%, the researchers pointed out.
During the past decade the pendulum in the U.S. has swung dramatically away
from VBAC delivery toward repeat cesarean section, and the 1999 ACOG
revision may have accelerated this trend, Dr. Zweifler said. Nevertheless,
he added, in 2002 California births constituted 13.1% of U.S. deliveries.
"We recommend that a balanced presentation of risks and the encouraging
outcomes found in this analysis be included in discussions with pregnant
women who have had a previous cesarean section," Dr. Zweifler's team
advised.
An evidence-based approach to VBAC delivery, he said, may lead to further
refinements in these guidelines.
Primary source: Annals of Family Medicine
Source reference:
John Zweifler, et al "Vaginal Birth After Cesarean in California: Before and
After a Change in Guidelines," Annals of Family Medicine 2006;4:228-234.
Leanne Wynne
Midwife in charge of "Women's Business"
Mildura Aboriginal Health Service Mob 0418 371862
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