Do Epidurals Increase Cesareans?

If you ask most doctors and more than a few midwives whether epidurals increase cesareans, the answer will be a hard “No,” followed by, “Research evidence has shown that they don’t.”

I’m here to say, “Not so fast.” I think we have equally strong evidence that they do.

Let’s look at the case for and against epidurals increasing cesarean surgeries. I’ll finish up with my usual “Take-Away” section with ways to counteract that effect if my evidence is correct.

The Case against Epidurals Increasing Cesareans

The argument that epidurals don’t increase cesareans goes something like this:

Back when epidurals were first becoming popular, studies began reporting that more women having epidurals had cesareans than women who didn’t. The problem was, though, that you can’t tell whether this had something to do with epidurals or whether women having difficult labors—and who were therefore more likely to have cesareans—were also more likely to want an epidural.

To answer this question, investigators began conducting randomized controlled trials (RCTs). These are studies in which participants are assigned by chance, i.e., randomly, to one form of treatment or another. Unlike studies analyzing data after the fact, RCTs start with similar groups who are assigned by chance to have, or avoid having, an epidural during labor. Random assignment enables investigators to determine which is cause and which is effect since participants in both groups are equally likely to have difficult labors. Data from multiple RCTs can also be pooled for analysis, which further strengthens their conclusions. Pooled analysis of the RCTs of epidural analgesia finds that epidurals do not increase cesareans.¹

Case closed—or is it?

Rebuttal

Logically, you would expect epidurals to increase cesareans. They tend to slow labor—hence the increased need for IV oxytocin to put labor back on track¹⁸—and they increase the probability of the baby persisting in an unfavorable position for descending through the pelvis (persistent occiput posterior).^{1, 5, 7, 16, 19} They also increase the probability of maternal fever,¹⁰ and developing a fever in a slowly progressing labor would be likely to tip the scale toward cesarean delivery.

Logic notwithstanding, pooled analysis of RCT data didn’t find an increase. Does that close the case? Maybe not.

To begin with, trial results were analyzed according to assignment group, not actual treatment. Analysis according to planned treatment, not what participants actually did, is standard in RCTs because to do otherwise would undo the main advantage of RCTs, which is assignment to treatment group according to chance. As you might expect, though, in many of the trials, substantial numbers of women assigned to the “no epidural” group actually had one. This crossover puts a thumb on the scale in trying to determine whether epidurals increase cesareans, and the more participants having epidurals in the “no epidural” group, the heavier the thumb. A group of researchers evaluated the effect of this “thumb” on the results of the epidural RCTs. They applied a statistical analysis technique that compensates for the effect of crossover, and they found that, yes, epidural analgesia probably did, in fact, increase the probability of cesarean delivery.³

RCTs have another weakness as well. RCTs are generally conducted in academic centers in a hothouse environment of rules, protocols, and strict supervision. That means their results may not apply to the real-world conditions of the typical hospital and obstetrician.

So we have reason to believe that data from randomized controlled trials may be misleading and their finding that epidurals don’t increase cesareans can’t be taken as gospel. This casts doubt on the systematic review’s conclusion, but it isn’t conclusive. We still need studies contradicting it. This brings us to . . .

The Case for Epidurals Increasing Cesareans

As it turns out, we have a relatively new trial design that addresses the “chicken and egg” problem of analyzing outcomes after the fact:  propensity score matching. This technique, like random assignment, accounts for the possibility that the adverse outcome is related to the reason for having the treatment, not the treatment itself. It works like this: investigators construct a propensity score using factors associated with both how likely each study participant would be to have the treatment and with increased likelihood of the outcome. In the case of studies of epidural versus no epidural, the factors are such things as induced labor, first birth, high birthweight, etc.; the treatment is an epidural; and the outcome is a cesarean. They then create matched pairs according to their scores in which one member of the pair has the treatment and the other doesn’t and compare outcomes between the pairs.

At the time that my book Labor Pain: What’s Your Best Strategy? went to press, I had two propensity score studies. As of last month, now there’s three, all finding higher cesarean rates in women who had an epidural compared with women with matching propensity scores who didn’t: 15% vs. 5%, 20% vs. 8%; 14% vs. 9%.^{2, 6, 15}

In other words, we have three studies of epidural use under every-day conditions that contradict the RCTs and that like RCTs, account for the possibility that more difficult labors are responsible for the association between epidurals and increased cesareans.

The Take-Away

Let’s say the propensity score studies have it right. Where does that leave you if your preference is to plan an epidural?

If you have had a prior vaginal birth, not to worry. You’re pretty much in the clear. Factors that slow progress are much more of a concern in first-time mothers because they are more prone to have problems with progress and are therefore more vulnerable to any adverse effect of epidurals.

But what if this is your first baby?  As I wrote above, there are ways to counteract their effect on cesareans. First and foremost is this one:

• Choose a care provider with a low cesarean rate. Studies have shown that individual practice style overrides any effect of epidurals.^{4, 9, 11, 13, 17} The simplest indicator of practice style is cesarean rate. Practitioners who have vaginal birth as a goal will have more patience and will manage labor and epidurals differently from those who are indifferent to whether labor ends in a cesarean. (As a sidenote, practice style may be another reason why RCTs didn’t find a difference in cesarean rates. If your care provider has a high cesarean rate, it makes little difference whether you have an epidural or you don’t.)

As for what’s a low cesarean rate, in a mixed population of women having first babies, women with previous vaginal births, and women with previous cesareans, research has found that the sweet spot is between 10% and 15%.⁸ You aren’t likely to find an obstetrician these days with rates that low—the US cesarean rate is 32% and has been for more than a decade—but I’d take anything above the low 20 percents as a red flag. A midwife’s rate should be substantially lower as they only take clients at low risk for cesarean.

The hitch is that almost all doctors and midwives work in group practices and rotate call for attending births, and members of the same practice may have widely differing cesarean rates. And in some cases, staff obstetricians called hospitalists may manage all deliveries, which means the people you see in pregnancy won’t be attending the birth. Here, then, are a couple of things you can do for yourself:

• Hire a doula. A doula will have ideas and strategies for helping labor progress in women with epidurals. Be sure, though, she is on the same page as you about your having one.
• Delay an epidural until at least 5 cm dilation. This has two advantages:

First, as I wrote above, epidurals slow labor, and more babies persist in the unfavorable occiput posterior position. Staying active and mobile in early labor could help labor progress and help an occiput posterior baby rotate from facing your belly to facing your back. Once in active labor with a baby well positioned for birth, an epidural would be less likely to slow things down. Some studies confirm that starting an epidural in early labor increases the odds of cesarean,^{12, 14, 21} while others disagree.²⁰ Still, most labors aren’t that intense in the early phase of dilation. You have nothing to lose and possibly something to gain by holding off until active labor kicks in.

Second, as I also wrote above, epidurals can cause maternal fever, and likelihood of fever correlates with epidural duration.¹⁰ Delaying an epidural until more advanced labor would shorten epidural duration.

References

1. Anim-Somuah M, Smyth RM, Cyna AM, et al. Epidural versus non-epidural or no analgesia for pain management in labour. Cochrane Database Syst Rev 2018;5:CD000331.
2. Bannister-Tyrrell M, Ford JB, Morris JM, et al. Epidural analgesia in labour and risk of caesarean delivery. Paediatr Perinat Epidemiol 2014;28(5):400-11.
3. Bannister-Tyrrell M, Miladinovic B, Roberts CL, et al. Adjustment for compliance behavior in trials of epidural analgesia in labor using instrumental variable meta-analysis. J Clin Epidemiol 2015;68(5):525-33.
4. Beilin Y, Friedman F, Jr., Andres LA, et al. The effect of the obstetrician group and epidural analgesia on the risk for cesarean delivery in nulliparous women. Acta Anaesthesiol Scand 2000;44(8):959-64.
5. Cheng YW, Shaffer BL, Caughey AB. Associated factors and outcomes of persistent occiput posterior position: A retrospective cohort study from 1976 to 2001. J Matern Fetal Neonatal Med 2006;19(9):563-8.
6. Fieni S, di Pasquo E, Formisano D, et al. Epidural analgesia and the risk of operative delivery among women at term: A propensity score matched study. Eur J Obstet Gynecol Reprod Biol 2022;276:174-8.
7. Fitzpatrick M, McQuillan K, O’Herlihy C. Influence of persistent occiput posterior position on delivery outcome. Obstet Gynecol 2001;98(6):1027-31.
8. Goer H. Dueling cesarean statistics: What should the cesarean rate be? — Henci Goer compares recent studies. In: Muza S, ed. Science and Sensibility: Lamaze International; 2015.
9. Guillemette J, Fraser WD. Differences between obstetricians in caesarean section rates and the management of labour. Br J Obstet Gynaecol 1992;99(2):105-8.
10. Jansen S, Lopriore E, Naaktgeboren C, et al. Epidural-Related Fever and Maternal and Neonatal Morbidity: A Systematic Review and Meta-Analysis. Neonatology 2020;117(3):259-70.
11. Janssen PA, Klein MC, Soolsma JH. Differences in institutional cesarean delivery rates-the role of pain management. J Fam Pract 2001;50(3):217-23.
12. Klein MC. Does epidural analgesia increase rate of cesarean section? Can Fam Physician 2006;52:419-21, 26-8.
13. Klein MC, Grzybowski S, Harris S, et al. Epidural analgesia use as a marker for physician approach to birth: implications for maternal and newborn outcomes. Birth 2001;28(4):243-8.
14. Lieberman E, Lang JM, Cohen A, et al. Association of epidural analgesia with cesarean delivery in nulliparas. Obstet Gynecol 1996;88(6):993-1000.
15. Nguyen US, Rothman KJ, Demissie S, et al. Epidural analgesia and risks of cesarean and operative vaginal deliveries in nulliparous and multiparous women. Matern Child Health J 2010;14(5):705-12.
16. Ponkey SE, Cohen AP, Heffner LJ, et al. Persistent fetal occiput posterior position: obstetric outcomes. Obstet Gynecol 2003;101(5 Pt 1):915-20.
17. Segal S, Blatman R, Doble M, et al. The influence of the obstetrician in the relationship between epidural analgesia and cesarean section for dystocia. Anesthesiology 1999;91(1):90-6.
18. Shmueli A, Salman L, Orbach-Zinger S, et al. The impact of epidural analgesia on the duration of the second stage of labor. Birth 2018;45(4):377-84.
19. Sizer AR, Nirmal DM. Occipitoposterior position: associated factors and obstetric outcome in nulliparas. Obstet Gynecol 2000;96(5 Pt 1):749-52.
20. Sng BL, Leong WL, Zeng Y, et al. Early versus late initiation of epidural analgesia for labour. Cochrane Database Syst Rev 2014;10:CD007238.
21. Thorp JA, Hu DH, Albin RM, et al. The effect of intrapartum epidural analgesia on nulliparous labor: a randomized, controlled, prospective trial. Am J Obstet Gynecol 1993;169(4):851-8.