Dr Edwards is Professor and Chief, Section of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Oklahoma Health Sciences Center, Oklahoma City.
Prior to the 1980s, because labor after a previous cesarean delivery was believed to be dangerous, many obstetricians recommended repeat cesareans for all subsequent births to women with a previous such delivery. Since then, TOLAC has been advocated as a reasonable alternative for women with a previous cesarean delivery via a low transverse uterine incision.
You are covering the Labor and Delivery unit when a patient presents for a scheduled induction of labor. She is a 35-year-old African-American P1001at 40 weeks gestational age who had a prior cesarean delivery (CD) due to arrestof dilation at 8 cm. She is 5 ft 3 in tall and weighs 280 lb (body mass index [BMI] 50 kg/m2).
Her pregnancy has been uncomplicated, and the estimated fetal weight is 4000 g. Is trial of labor after cesarean (TOLAC) in this patientâs best interest? What if she were nulliparous and, therefore, did not have a history of a prior cesarean delivery?
Prior to the 1980s, because labor after a previous cesarean delivery was believed to be dangerous, many obstetricians recommended repeat cesareans for all subsequent births to women with a previous such delivery. Since then, TOLAC has been advocated as a reasonable alternative for women with a previous cesarean delivery via a low transverse uterine incision. Practice Bulletin No. 115 from the American College of Obstetricians and Gynecologists (ACOG) states that â â¦ a failed labor â¦ compared with vaginal birth after cesarean (VBAC), is associated with increased maternal and perinatal morbidity. Assessment of individual risks and the likelihood of VBAC is, therefore, important in determining who are appropriate candidates for TOLAC.â1
The statement is purposefully vague in order to define a range in standard of care, but what degree of risk is tolerable and what likelihood of VBAC success is needed for a patient to be an âappropriate candidateâ for TOLAC?
Twenty years ago, McMahon and colleagues published a population-based, longitudinal study of 6138 women in Nova Scotia who had a single prior cesarean delivery and delivered a live singleton infant during the study period. The overall rate of maternal complications did not differ significantly between women who attempted TOLAC (considering collectively both women having a VBAC and those requiring a repeat cesarean delivery after failed TOLAC) and those who elected a repeat cesarean delivery without labor. However, major complications (hysterectomy, uterine rupture, and/or operative injury) were almost twice as likely in the group who attempted TOLAC (again, considering collectively both women having a VBAC and those requiring a repeat cesarean delivery after failed TOLAC) (adjusted odds ratio [aOR] 1.8, 95% confidence interval [CI] 1.1â3.0).2
This difference was driven by the fact that major complications were 5 times as likely with failed TOLAC attempts compared to successful ones (aOR 5.1, 95% CI 2.8â9.4). Patients electing repeat cesarean delivery without labor had rates of major complications intermediate between the successful and unsuccessful TOLAC groups (Figure 1).2
Data from this and other studies contributed to the waning enthusiasm for VBAC in the United Statesâthe rate of VBAC in 1996 was 28%; it has been <12% every year since 2004.3
Because the likelihood of morbidity with TOLAC is inversely proportional to the likelihood of success (ie, vaginal delivery), it is helpful, when counseling patients about TOLAC versus repeat cesarean delivery without labor, to consider a womanâs individual likelihood of TOLAC success. A useful calculator is available from the Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal-Fetal Medicine Units (MFMU) Network at https://mfmu.bsc.gwu.edu/PublicBSC/MFMU/VGBirthCalc/vagbirth.html. This calculator takes into account the patientâs age, BMI, race/ethnicity, number of prior vaginal deliveries, and primary indication for previous cesarean delivery.4
Multiple studies have reported that morbid obesity is a risk factor for failed TOLAC. Using an unconventional definition of >300 lb at the first prenatal care visit, Chauhan et al. reported a VBAC success rate of only 13% in morbidly obese women and recommended repeat cesarean delivery without labor in such patients.5,6 Using a more conventional definition of morbid obesity (BMI â¥40 kg/m2 at the first prenatal visit), Edwards et al. reported a VBAC success rate of 57%.
However, despite success among most patients who attempted TOLAC, puerperal infections were 3 times as likely in the TOLAC group compared to the elective repeat cesarean delivery group, and there was no cost benefit to TOLAC compared with elective repeat cesarean delivery.7
Hibbard et al. reported that, in women with a BMI â¥40, composite maternal morbidity (OR 1.9; 95% CI 1.5â2.6) and neonatal injury (OR 5.1; 95% CI 1.9â13.8) are more likely with TOLAC compared to elective repeat cesarean delivery.8 Similar to the data from McMahon and colleagues from the general population, the highest risk of morbidity was with failed TOLAC, highlighting the need to undertake TOLAC only if a patient has a reasonably high likelihood of success.
Of note, according to the MFMU VBAC calculator, the patient in the case at the beginning of this article would have a 12.8% likelihood of delivering vaginally.
We know that morbid obesity is associated with an increased risk of labor induction, induction failure, and cesarean delivery.9-14 Because these outcomes are increased, obesity also is associated with increased risks of clinical chorioamnionitis, postpartum hemorrhage, wound infections, surgical complications, and increased neonatal morbidity (Figure 2).10,15-17
In addition, even lesser degrees of obesity (BMI 30â39) have been independently associated with postterm pregnancy, induction of labor, and cesarean delivery after postterm labor inductions.18-22
A randomized controlled trial would be the ideal study for comparing planned cesarean delivery to induction of labor for morbidly obese women who do not spontaneously labor. However, the feasibility of such a study is questionable at best.
Subramaniam et al. recently published a cohort study evaluating women with singleton pregnancies, a BMI â¥40, and delivery via either cesarean without labor or after labor induction. Sixty-five percent of the induction group had cervical ripening, and the cesarean delivery rate in the induction group was 41%. A composite of maternal morbidities occurred in 18.2% of the women who delivered vaginally after labor induction, 45.4% of those who had a cesarean delivery after an unsuccessful labor induction, and 24.4% who had a planned cesarean delivery without labor. After multivariable adjustments, maternal morbidity (aOR 0.98; 95% CI 0.55â1.77) was similar in women delivered by planned cesarean compared to the overall group delivered after inductions (both patients who delivered vaginally and those having a cesarean delivery after a failed induction).23
Neonatal morbidity followed a similar patternâthe neonatal morbidity composite occurred in 8.1% of the women who delivered vaginally after labor induction, 20.9% of those who had a cesarean delivery after an unsuccessful labor induction, and 10.3% who had a planned cesarean delivery without labor.
After multivariable adjustments, neonatal morbidity (aOR 0.81; 95% CI 0.37â1.77) was similar in women delivered by planned cesarean delivery compared to the overall group delivered after labor inductions (both patients who delivered vaginally and those having a cesarean delivery after a failed induction).23 As expected, the group with the highest risks of both maternal and neonatal morbidity were patients who underwent cesarean delivery after an unsuccessful labor induction (aOR 3.7; 95% CI 2.4â5.9 for maternal and aOR 3.0; 95% CI 1.6â5.5 for neonatal morbidity).
Using the same dataset, a cost minimization analysis showed that induction of labor in such patients is less costly than cesarean delivery without labor only if the chance of vaginal delivery is >57% (a cesarean delivery rate of <43%).24 Many subgroups of obese women have cesarean delivery rates in excess of 43%. Gunatilake et al. reported a 78% rate of cesarean delivery in women with a BMI â¥60.25 In a RCT of cervical ripening methods, Edwards et al. reported a 55% rate of cesarean delivery in women with a BMI â¥40 who started labor inductions with the dinoprostone insert.26
Previous cesarean delivery is a risk factor for placenta previa, placenta accreta, and hysterectomy in future pregnancies. Due to the fact that these complications are associated with previous cesarean delivery, the patientâs plans for future pregnancy should be considered when making decisions about delivery route. However, these complications are far less likely than the complications that drove the maternal morbidity composite in the above study by Subramaniam et al (puerperal infection, wound infection and/or disruption, postpartum hemorrhage, and hysterotomy extension).23
Until current trends reverse, clinicians will increasingly be faced with counseling morbidly obese women regarding their planned mode of delivery. In terms of morbidity risk, vaginal delivery is the preferred outcome for these women. However, cesarean delivery after labor is more morbid than cesarean delivery without labor.
Providers need a calculator similar to the MFMU VBAC calculator that is capable of assigning a likelihood of vaginal delivery for morbidly obese women undergoing induction of labor. If the chance of vaginal delivery was sufficiently low using such a calculator, a primary cesarean delivery without a labor attempt would be less costly and would pose less risk to both mother and child.
Development of such a calculator and evaluation of outcomes when patient care is guided by the results should be a research priority.
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21. Gilead R, Yaniv Salem S, Sergienko R, Sheiner E. Maternal âisolatedâ obesity and obstetric complications. J Matern Fetal Neonatal Med. 2012;25:2579-2582.
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23. Subramaniam A, Jauk VC, Goss AR, Alvarez MD, Reese C, Edwards RK. Mode of delivery in women with class III obesity: planned cesarean compared with induction of labor. Am J Obstet Gynecol. 2014;211:700.e1-9.
24. Subramaniam A, Corvey KJ, Kilgore ML, Edwards RK. Planned cesarean delivery compared to induction of labor in women with class III obesity: a cost-minimization analysis. J Matern Fetal Neonatal Med. 2015;1.5. [Epub ahead of print]
25. Gunatilake RP, Smrtka MP, Harris B, et al. Predictors of failed trial of labor among women with an extremely obese body mass index. Am J Obstet Gynecol. 2013;209:562.e1-5.
26. Edwards RK, Szychowski JM, Berger JL, et al. Foley catheter compared with the controlled-release dinoprostone insert: a randomized controlled trial. Obstet Gynecol. 2014;123:1280-1287.