A new study published in the journal BMC Pregnancy and Childbirth in March 2020 shows that labor proceeds successfully in more than 90% of cases and should be considered a reasonable option for mother and baby.
The study based in Japan’s Toyota Memorial Hospital was motivated by the increasing rates of Cesarean section worldwide, fueled in almost 50% of cases by a history of previous Cesarean delivery.
The researchers examined the health records of over 1,000 pregnant women who had had one or more prior Cesarean deliveries. The study period was from April 2005 to August 2017. They looked at whether the mother fulfilled the criteria for a trial of labor after Cesarean (TOLAC) in the present pregnancy. Women who were eligible for TOLAC were given a full description of the risks and advantages of both a repeat Cesarean section and TOLAC well before the date of delivery.
The most significant risk with a vaginal delivery after a previous Cesarean section is that the uterus might rupture along the line of the old Cesarean scar. On the other hand, a Cesarean itself has an associated risk of infection, hemorrhage, and other surgical complications. If the woman opted for TOLAC, she has a lower risk of the above complications, can avoid abdominal surgery, as well as a have a better prognosis for any future pregnancies. Multiple Cesareans can cause surgical complications like injury to the bladder and bowel, intractable bleeding requiring the removal of the uterus, and difficulties with placental adherence to the uterine wall, which lead to delayed or incomplete expulsion of the placenta.
The women were then required to think over the explanations given and decide which mode of delivery they wanted to pursue, by 34 weeks of pregnancy.
Explaining the rationale behind the current study, researcher Kaname Uno says, “Cesarean rates are increasing globally with almost half of decisions on whether to deliver by Cesarean based on previous Cesarean delivery. A trial of labor after Cesarean (TOLAC) is considered a safe option, but most eligible women instead undergo repeat Cesarean. This may be due to a lack of sufficient education on the risks and benefits of both types of delivery.”
Among the 735 pregnant women, about 470 wanted to have TOLAC, accounting for over 64%, while about 36% decided to have a repeat Cesarean. More than 91% of the women who chose TOLAC succeeded in having a successful vaginal delivery, at 430 women, but 41 of them had to have a Cesarean due to ‘failed TOLAC.’
The incidence of uterine rupture in this group was 0.6% (3 women); however, no harm occurred to either mother or infant in any pair. Failed TOLAC was more likely in women who suffered a premature rupture of membranes (PROM) or had a 40+ week pregnancy.
However, among all women who had one or more vaginal deliveries earlier, even if they had also had a Cesarean delivery at some point, over 96% of them had successful TOLAC.
Factors linked to a better TOLAC outcome
Earlier research has shown that some factors are associated with a higher rate of success in TOLAC: an increasing number of prior vaginal births after Cesarean (VBACs), the reason for the earlier Cesarean, the readiness of the uterus to enter labor at the time of admission, the need for labor induction and the weight of the fetus, as well as the mother’s weight and race.
If the earlier Cesarean was not because of a difficult delivery, if the woman entered labor spontaneously, the baby was of healthy weight, and the woman was white and non-obese. If she had already had at least one vaginal delivery, the TOLAC was more likely to be successful. A previous vaginal delivery also reduces the already low rate of uterine rupture in TOLAC. Overall, uterine rupture is associated with 1.4 additional deaths of babies for every 10,000 TOLAC cases. Other benefits include the cost-effectiveness of TOLAC vs. repeat Cesarean.
The current study supports existing evidence that women can safely labor after Cesarean rather than routinely opting for repeat Cesareans. According to Uno, such a decision is doubly beneficial because the pregnancy is likely to go on for a longer period, which in turn improves the health of the infant by reducing the risk of potential health complications.
The study concludes, “The results suggest that health professionals should be encouraged to have ongoing discussions with expectant mothers about the risks and benefits associated with each mode of delivery, allowing them to make their own informed choices.”
Limitations of the current study include the freedom given to each of the mothers to choose the preferred mode of delivery, which in turn determined the sizes of the TOLAC and the repeat Cesarean groups. Such decisions are based not only on medical explanations but on previous experiences, bias towards one or the other approach, and region of origin. As a result, the findings are not likely to be generalizable to all pregnant women with a history of Cesarean. Secondly, the very low incidence of uterine rupture may indicate the need for further studies to provide an accurate picture of this as one of the complications of TOLAC.
Uno, K., Mayama, M., Yoshihara, M. et al. Reasons for previous Cesarean deliveries impact a woman’s independent decision of delivery mode and the success of trial of labor after Cesarean. BMC Pregnancy Childbirth 20, 170 (2020). https://doi.org/10.1186/s12884-020-2833-2