A new paper published this month in the Canadian Medical Association Journal, Mode of delivery after a previous cesarean birth, and associated maternal and neonatal morbidity, shows that attempted vaginal birth after C-section (VBAC) significantly increases the risk of poor maternal and neonatal outcome.
Absolute rates of severe maternal morbidity and mortality were low but significantly higher after attempted vaginal birth after cesarean delivery compared with elective repeat cesarean delivery (10.7 v. 5.65 per 1000 deliveries, respectively; adjusted RR 1.96, 95% CI 1.76 to 2.19). Adjusted rate differences in severe maternal morbidity and mortality, and serious neonatal morbidity and mortality were small (5.42 and 7.09 per 1000 deliveries, respectively; number needed to treat 184 and 141, respectively).
The study confirms what we’ve known for sometime. Successful VBAC is safer than elective repeat C-section, which is much safer than failed VBAC.
[pullquote align=”right” cite=”” link=”” color=”” class=”” size=””]Should we be so desperate to lower the C-section rate?[/pullquote]
The authors explain:
Vaginal birth after cesarean delivery is increasingly contentious as rates of cesarean delivery rise and prior cesarean delivery serves as the most common single indication for a cesarean delivery. Planning mode of delivery for women with a previous cesarean delivery is challenging both for the patient and the care provider. An elective repeat cesarean delivery is associated with an increased risk of surgical complications, as well as an increased risk of abnormal placentation in subsequent pregnancies. On the other hand, attempted vaginal birth after cesarean delivery is associated with a higher risk of uterine rupture and other maternal and infant complications.In addition, a substantial proportion of women attempting a vaginal birth after cesarean delivery will require an emergency cesarean delivery, which increases the risk of maternal and infant complications.
The question is: should this matter to our desperate efforts to lower the C-section rate?
We are currently living through a moral panic about the C-section rate. To hear partisans of “normal” birth tell it, the current C-section rate of 32% is nothing short of a medical scandal even though there is considerable evidence that C-section rates of over 40% are entirely compatible with low rates of maternal and neonatal mortality and morbidity. Nevertheless we are continually exhorted that the C-section rate must be reduced.
One of the ways to reduce the current C-section rate would be to increase the rate of attempted VBAC. VBAC rates were essentially 0% back when all incisions on the uterus were vertical. Because of the high risk of uterine rupture in a subsequent labor, the mantra of “once a Cesarean, always a Cesarean” held sway. As horizontal incisions on the uterus became standard of care, and the rupture rate dropped dramatically, VBAC became quite popular. When I was practicing I, like my colleagues, offered a VBAC to every woman with one previous C-section. Nearly 80% of the attempted VBACs were successful.
In the 1990’s large scale data collection, along with spectacular malpractice settlements, demonstrated that the risk of ruptured uterus after a previous horizontal uterine incision was dramatically smaller, it was emphatically not zero. This study confirms those findings.
The authors note:
The evaluation and interpretation of risks associated with attempted vaginal birth after cesarean delivery presents a challenge because risk perspectives vary widely. Both the relative increase in rates of severe maternal and neonatal morbidity and mortality after attempted vaginal birth after cesarean delivery compared with elective repeat cesarean delivery and the absolute difference in these rates need to be weighed carefully before a decision is made about whether the excess risks are acceptable or high. In additional, women planning large families need to be cognizant of the risks of morbid placentation in subsequent pregnancies, because such risks increase with repeated cesarean deliveries. These inputs into decision-making may also be affected by desire for vaginal birth, the severity of the outcomes in question and other personal valuations. Health care providers need to help women to contextualize risks better so that they are able to make informed and personalized decisions.
There is nothing wrong with a high C-section rate in and of itself. A high C-section rate is perfectly compatible with low rates of maternal and neonatal mortality and morbidity. Every woman should be counseled that successful VBAC is safer than elective C-section, which is much safer than failed VBAC. However, the chance of successful VBAC varies from women to woman and from pregnancy to pregnancy and that, too, will be a factor in decision making.
Different women will assess the importance of individual risks differently. The job of obstetricians is NOT to lower the C-section rate but rather to deliver healthy babies to healthy mothers while respecting women’s right to make decisions about their own bodies. It is never appropriate to privilege a process — in this case vaginal birth — over the outcome.
