In response to the recent New England Journal of Medicine article “A Randomized Trial of Planned Cesarean or Vaginal Delivery for Twin Pregnancy,” Michael Greene, chief of obstetrics at Massachusetts General Hospital in Boston, published an accompanying editorial, “Delivering Twins.” As I mentioned in my previous post, you must have a subscription to NEJM to read the editorial (or have access to a library that does). I am going to offer some analysis here anyway. This post is a little technical because the editorial is from a medical journal. But read on–it’s important stuff!
A quick primer: An RCT is a randomized control trial. It is the gold standard for evidence based medical practice. People who meet the criteria to be in a study are put into two groups by random assignment (like a lottery or counting them off 1, 2, 1, 2). One group gets the usual treatment and the other group gets the treatment that is being tested. Then the researchers use statistical testing to see if the people who got the new treatment had better outcomes than the people who got the usual treatment. If the outcomes are the same, we might look to see if one of the treatments has other advantages, such as lower cost.
Now for the analysis:
Greene’s editorial excuses current practice from thoughtful debate and offers conjecture on why planned cesarean is a better route for twin deliveries despite the evidence from the RCT.
In his first paragraph, Greene explains the rise in twin pregnancies, which are more likely in older mothers and women who get pregnant through assisted reproductive technologies. Both of these circumstances have become more common.
He then discusses the rise in cesarean rates (under 5% in the 1960s, around 21% in the mid 1990s, but almost 33% today), and particularly the rise in cesareans for twins (around 54% of twins were delivered by cesarean in the mid 1990s, but around 75% are today). We then get this statement:
Although the national perinatal mortality rate has fallen steadily during this time, from 14.6 deaths per 1000 births in 1985 to 10.5 deaths per 1000 births in 2006, it remains legitimate to ask whether all those cesarean deliveries were necessary to ensure the lowest possible maternal and perinatal morbidity and mortality.
First, Greene conflates correlation and causation, an error scientists loathe in the general public. Recent studies have not attributed declines in perinatal death to an increase in cesarean section–not even through correlation. The CDC notes that much of the decline in perinatal death is decline in fetal death, which implies that there is better prenatal care for women, which allows for conditions that can cause fetal demise (e.g. uncontrolled diabetes) to be treated more effectively. Perinatal death is also reduced by developments in neonatal care, as evidenced by the steadily declining age of fetal viability. In fact, having had a previous cesarean is linked to an increase in perinatal death rates.
The second (and perhaps more egregious) aspect of this statement is that it does not point out that maternal mortality has nearly doubled during the same period, making the United States one of the most dangerous developed nations for birthing mothers despite having the highest childbirth costs in the world. While there is no definitive link between decreased perinatal mortality and cesarean for the period Greene cites, there is a link between maternal mortality (and morbidity) and cesarean during this period. It is true that maternal death is much rarer than infant death, so the absolute risk for women is small, despite the relative risk being high (see this post for an explanation of absolute vs relative risk). However, physicians generally consider relative risk very seriously when it comes to infant outcomes, as evidenced by the intense antipathy most obstetricians have for planned home birth.
It seems if Greene were keeping up with literature, he would be aware that the question he says is “legitimate” to ask–“whether all those cesarean deliveries were necessary”–has already been answered.
Greene goes on to note that “many, but not all” observational studies have indicated that planned cesarean for twin births is preferable. He goes on to note that
…these observational studies are inevitably vulnerable to criticisms regarding potential biases and inadequate adjustment for relevant covariates.
He then goes on to explain that the new study is a randomized control trial (RCT). The RCT is the gold standard of medical research. Cochrane reviews (which set international standards for evidence-based care) generally base their recommendations on the results of RCTs. ACOG puts practice guidelines into three categories, with “A” being the highest ranked. “A” guidelines are based on evidence from RCTs.
After giving an overview of the study design and results, Greene asks,
How should patients and practitioners view the results of this study, which showed no significant differences in important fetal, neonatal, or maternal outcome measures on the basis of the planned route of delivery?
His response is that many women delivering twins would up having cesareans even if they planned for vaginal birth (of course, this happens to a large number of women with uncomplicated singleton pregnancies as well). He then offers this zinger:
the results of this study suggest that a plan to deliver appropriately selected sets of twins vaginally is a reasonably safe choice in skilled hands.
First of all, the study already put limits on cases where vaginal birth should be considered, the primary condition being that the first twin had to be head down (the second twin could be head down or breech). Why the caveat about “reasonably safe”? The study found that planning a vaginal birth is just as safe as planning a cesarean birth under the the criteria specified in the study. And what is this about “skilled hands”?–is he implying that many obstetricians aren’t skilled? Delivering twins, as he pointed out earlier, is an increasingly frequent occurrence. Why would OBs not be trained in this important skill? About 10% of the planned cesareans in the study wound up being vaginal deliveries, indicating that an OB must be prepared to deliver twins vaginally even when a cesarean is planned. The chain of logic then indicates that if the OB’s hands aren’t skilled enough to do a vaginal delivery of twins, the obstetrician should not be caring for women with twin pregnancies.
Greene then goes on to suggest that the study did not have enough power to detect very rare occurrences that (he believes) would show cesarean to be the safer route. This is disheartening, as doctors often cling to technocratic practice in spite of copious evidence from observational studies, saying that they can only trust the results of an RCT. Here, we have the opposite–the observational studies offered some support for planned cesarean over planned vaginal birth, and the RCT does not. But Greene still suggests that current practice should continue in accordance with the findings of the observational studies. His response offers further indication that many obstetricians privilege technology over science and choose to remain entrenched in current practices in the face of contrary evidence (an idea also reinforced by the article’s accompanying video featuring supine birthing positions). For Greene (and many other American OBs), technocratic practice is normal , and “natural” (physiologic/normal/biological) practice is the deviation.
Greene also does not discuss costs. In general, cesareans are far most costly than vaginal births, so if the outcomes are identical, why would one have a preference for the more expensive option?
Jon Barrett, the lead on the research study, was “dismayed” by Greene’s response and said, “Rather, I hope the findings will be a wake-up call, a reminder that natural birth should be the preferred option.” Amen, Dr. Barrett.
And perhaps, most important of all, both Dr. Greene and Dr. Barrett should mention the importance of giving women information to make their own decisions.