Why Doesn’t Anyone Believe the Research on Epidurals and C-sections?
Blame study design and limitations.
As we discussed in our post— Does Getting an Epidural Raise Your Risk of C-section? —studies on how epidurals affect the C-section rate present a conundrum. In the early 1990s, observational studies found a much higher chances of a C-section among women laboring with an epidural. But subsequent natural studies and randomized controlled trials (RCTs) have found no impact.
Many factors—changes to epidurals themselves, changes within hospitals, problems with observational studies — could contribute to the radical shift in evidence.
Here we want to examine the explanation many natural birth advocates favor: That recent randomized controlled trials (RCTs) get it wrong.
RCTs are generally conisdiered the gold standard for medical reseach. But this argument is not as outlandish as it may sound. RCTs do have serious drawbacks when it comes to studying epidurals, mainly because it’s really darn hard to deny women pain relief during labor.
Why RCTs may be flawed:
1. Participating in a randomized trial may alter doctor behavior.
Blinding, or preventing participating subjects and doctors from knowing whether a patient is assigned to the experimental or control group, Is a common practice in RCTs. But when it comes to studying epidurals, it is clearly impossible. It’s obvious whether a laboring woman has an epidural.
How could this knowledge affect the trial? Doctors might be extra cautious before performing c-sections for slow labors. They might be extra incluned to explore alternatives to C-sections, like waiting or assisting delivery with the vacuum or forceps. Both would be consistent with the finding that women given epidurals in these trials have higher rates of assisted deliveries but not of c-sections.
2. The hospitals where RCTs are conducted may differ from most hospitals.
The overall c-section rates for these hospitals are between 10–15%. This is markedly lower than the national average of 32%. It seems possible that these hospitals’ labor management practices differ from those of most U.S. hospitals.
3. Most RCTs compare epidurals with opiates as opposed to natural labor.
Why? Because researchers cannot ethically withhold pain relief from women in labor.
One study’s researchers did refuse to provide an epidural until a woman’s third request. (Whether this amounted to scientific heroism or callousness, I can’t decide.)
But in the vast majority of studies researcher yield to a woman’s first request for pain relief — and who can blame them?
To try to circumvent this problem, most RCTs compare epidurals not with natural labor, but with IV-administered opiates. But since opiates may also slow down labor and boost C-section rates, as some natural birth advocates have argued, they may provide a poor or biased comparison.
However, even RCTs comparing epidurals with natural labor find no impact on C-sections. So this concern is unlikely to cause major bias.
4. Randomization in these trials is imperfect.
Between 20–30% women in these trials assigned to receive opiates instead end up receiving an epidural, while 20–30% of women assigned to receive an epidural never receive one.
This type of cross-contamination is a real problem, and it could water down the effects of the randomization.
That said, the kind of cross-contamination is unlikely to account for the vast differences between early observational studies and recent RCTs, because even comparing women who actually receive epidurals and those who do not finds little impact on C-section rates.
Summing Up
RCTs on epidurals and C-sections have many flaws. But despite these flaws, the evidenc as a whole suggests that epidurals do not inevitably raise C-section rates. Visit (or revisit!) my first post to see how RCTs fit with what else we know about epidurals and C-sections.
Originally published at bloomlife.com.
