Is breech vaginal delivery safe?

Between 3-4% of babies begin labor in the breech (bottom first) position, increasing the risk of neonatal morbidity and mortality. Pre-emptive C-section has become the preferred method of delivery for breech babies, but now some are questioning this recommendation. The controversy is fueled by differing appraisals of the danger and by differing assessments of the whether any risk of neonatal death can be justified in the age of the safe Cesarean.

The best conducted and most important study comparing breech vaginal delivery with elective C-section is the Term Breech Trial (TBT) conducted by Mary Hannah and colleagues. It is the only randomized control trial of its kind.

… [W]e found that the fetuses of women allocated planned caesarean section were significantly less likely to die or to experience poor outcomes in the immediate neonatal period than the fetuses of women allocated planned vaginal birth. Although some of the deaths in the planned vaginal birth group were related to difficulty with vaginal breech delivery, others were clearly associated with problems during labour. Thus the avoidance of labour and vaginal breech delivery could have contributed to better outcomes with planned caesarean section…

A more recent trial, the PREMODA (PREsentation et MODe d’Accouchement: presentation and mode of delivery) study produced different findings and as a result, some obstetricians have been calling for a re-evaluation of the standard recommendation for C-section delivery of a breech baby.

The groups [planned vaginal delivery vs. planned C-section] did not differ significantly for the combined outcome of fetal or neonatal mortality or serious morbidity (odds ratio [OR] = 1.10, 95% CI [0.75-1.61]. Of the criteria included in this combined variable, only a 5-minute Apgar score less than 4 was significantly more frequent in the planned vaginal group (n = 4 vs n = 1, OR = 8.9, 95% CI [1.00-79.8]). Of the other individual outcomes, the following were significantly more frequent in the planned vaginal than in the planned cesarean group: 5-minute Apgar score less than 7 (OR = 3.2, 95% CI [1.9-5.3]), total injuries (OR = 3.9, 95% CI [2.4-6.3]), and intubation (OR = 1.8, 95% CI [1.08-3.1]).

The authors of the PREMODA study acknowledge that their trial was not randomized and that the results must applied with caution. Nonetheless, the authors concluded:

In centers where planned vaginal delivery remains a widespread practice and in complying with rigorous conditions before and during labor, we did not find a significant excess risk associated with planned vaginal delivery compared with planned cesarean for women with a singleton fetus in breech presentation at term. There may be a slightly higher neonatal risk associated with planned vaginal delivery but it is very different from that reported in the only published large randomized trial….

In light of the PREMODA study, some obstetricians have been calling for a return to breech vaginal delivery. The NNT to prevent neonatal death from breech is 111. That translates to 110 unnecessary (in retrospect) C-sections for every baby saved. What are the risks of those C-sections? They include hemorrhage, transfusion and possible hysterectomy. Maternal mortality after elective C-section is so rare that many contemporary studies of C-section focus exclusively on morbidity.

So why not simply explain the controversy to patients, as well as the differing findings and let them choose? Putting aside the issue of the magnitude of the risk, are patients capable of giving informed consent to a procedure that will, if widely offered, lead to preventable neonatal deaths? Obviously consent ultimately rests with the patient, but can it be truly informed consent?

Let’s assume for the moment that The Term Breech Trial is correct and the excess risk of neonatal mortality in breech vaginal delivery is 9/1000. That sounds like a small number and many women will reason that the number is so small that they need not worry that their babies will die.

However, 9/1000 means that approximately 9 babies per 1000 WILL die. In the US approximately 140,000 babies each year present as breech at the onset of labor. Not all will meet the eligibility criteria for vaginal delivery (approximately 35% of breech babies are in an unfavorable position for vaginal delivery, and others will exceed the weight criteria or have other contraindications), but even if only half were eligible, that would mean 70,000 attempted breech vaginal deliveries. At an excess rate of neonatal mortality of 9/1000, we could expect that 630 babies would die from preventable neonatal deaths each year.

This is a relatively small number. Indeed, it would barely impact overall neonatal mortality figures (approximately 18,000 neonatal deaths per year), since the bulk of neonatal mortality is due to prematurity and congenital anomalies. On the other hand, that is quadruple the number of deaths we would expect in an otherwise low risk group. Most importantly, that number represents 630 sets of bereaved parents who would have had a healthy baby had they opted for elective C-section. Would those parents accept a preventable death philosophically, or would they be shocked and bewildered that the baby actually died? Would they simply try again or will they look for someone to blame?

Can the excess risk of neonatal mortality can be reduced somewhat by making the eligibility criteria more strict as the authors of the PREMODA study suggest? Only a randomized trial can provide that information, and unless the excess neonatal mortality rate could be reduced dramatically, we would still anticipate the preventable death of hundreds of babies per year.

C-section is not a trivial procedure, but it is an extremely safe surgery, reducing risk to the baby and only slightly elevating risk to the mother. Even though the risk of breech vaginal delivery is small, the outcome can be catastrophic. A lot of unnecessary (in retrospect) C-sections are being done. Do we think that is too high a price to pay to save several hundred babies each year?

Posted in: Obstetrics & gynecology, Science and Medicine

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