Morbidly obese gravidas: Labor or not?

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 patient’s best interest? What if she were nulliparous and, therefore, did not have a history of a prior cesarean delivery?

TOLAC in the general population

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 “ … a failed labor … 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.”¹

More: What links stillbirth and obesity?

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 “appropriate candidate” 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] 1.1–3.0).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 2.8–9.4). 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 States—the rate of VBAC in 1996 was 28%; it has been <12% every year since 2004.³

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