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Does Epidural Analgesia Predispose to Persistent Occiput Posterior?

February 14th, 2013 by avatar

Photo by Patti Ramos Photography

In my January Science and Sensibility blog post, I answered the question “Can We Prevent Persistent Occiput Posterior?” but because it wasn’t relevant to the study that prompted the post, and the piece was already long, I didn’t look at the role of epidural analgesia. Let me now rectify that.

All five studies examining the relationship between epidural analgesia and persistent occiput posterior (OP) find an association between them. Three studies compared women with an epidural versus no epidural according to whether they had an OP baby at delivery and found that 4 to 10 more women per 100 having an epidural had an OP baby at delivery (Cheng, 2006; Lieberman, 2005; Sizer, 2000). The other two compared women with an OP baby at delivery according to whether they had an epidural and found that 13 and 27 more women per 100 with a persistent OP baby had an epidural (Fitzpatrick, 2001; Ponkey, 2003).

Their results, however, aren’t sufficient to convict epidurals because we can’t tell whether having an epidural led to persistent OP or more painful and prolonged OP labor led to having an epidural. Investigators in one of the five studies argued for OP labor coming first on the grounds that while epidurals were more common in women with an OP baby at delivery than in women with an OA baby at delivery (74% vs. 47%) at their institution, a rise in epidural use from 3% in 1975 to 47% in 1998 had, if anything, decreased the hospital’s overall rate of persistent OP (4% vs. 2%) (Fitzpatrick, 2001). This must mean that as epidurals became more freely available, women having difficult OP labors were more likely to opt for one. Epidurals were the result, not the cause, of persistent OP. On the other hand, we have some corroborating evidence for their guilt. For one thing, back pain is thought to be a major reason why women with OP babies are more likely to want epidurals, but it turns out that back pain isn’t unique to OP. Serial sonograms reveal that virtually identical percentages of women laboring with an OA baby report back pain (Lieberman, 2005). For another, three of the five studies took into account other factors associated with difficult labor such as labor induction, labor augmentation, and birth weight and still found that epidurals were an independent risk factor for persistent OP (Cheng, 2006; Lieberman, 2005; Sizer, 2000).

Nevertheless, evidence from observational studies isn’t strong enough to close the case. As I noted, observational studies can determine association but not causation. In addition, investigators may not be able to identify all the confounding and correlating factors that affect outcomes. For a more definitive answer, we need experimental studies. This brings us to randomized controlled trials (RCTs), in which participants are randomly allocated to one form of treatment or the other, and to meta-analysis of RCTs, in which statistical techniques are used to pool data from more than one trial.

The Cochrane systematic review of epidural versus no epidural in labor pools data from four RCTs (673 women overall) that reported on persistent OP (Anim-Somuah, 2011). Five more women per 100 assigned to the epidural group had a persistent OP baby, but meta-analysis found that the difference just missed achieving statistical significance. The risk ratio was 1.4, meaning a 40% increased risk of persistent OP in women assigned to the epidural group compared with women assigned to the no-epidural group, but the 95% confidence interval ranged from 1.0 to 2.0, meaning a 95% probability that the true value lies between no increase (ratio of 1:1) and double the risk (2.0). However, a problem with the RCTs of epidural versus no epidural is that substantial percentages of women assigned to the no-epidural group actually had epidurals, but, as is prescribed in RCT data analysis, they were kept in their original group. In two of the four trials (204 women), though, 10% or less of women assigned to the no-epidural group had epidurals. If we calculate the excess rate of persistent OP in these two trials, we find that the gap widens to 9 more women per 100 with epidurals having a persistent OP baby. We don’t know whether this difference would achieve statistical significance, but the fact that the excess is in the same range as reported in the observational studies (4 to 10 more per 100) gives confidence in its validity.

Patti Ramos Photography

We also have two studies that suggest that the timing of the epidural may matter. One, of 320 women, reports that, after controlling for age, induction of labor, and birth weight, initiating an epidural at fetal station less than zero (above the ischial spines) resulted in 16 more women having a persistent OP or occiput transverse (OT) baby compared with initiation at 0 station or greater (at or lower than the ischial spines), an excess that rose to 20 more per 100 in first time mothers (Robinson, 1996). The other study analyzed outcomes in 500 first-time mothers according to whether an epidural was administered early (at or before 5 cm dilation), late (after 5 cm dilation), or not at all (Thorp, 1991). Seventeen more women per 100 in the early group had a persistent OP or OT baby compared with women in the late-epidural group, and 12 more had a persistent OP or OT baby compared with the no-epidural group, but rates were similar in women in the late and no epidural groups.

Taken all together, we may not have absolute proof of epidural culpability in predisposing to OP, but if I were on the jury, I would vote them “guilty as charged.”

Take home: Even without certainty, the precautionary principle dictates recommending to women desiring an epidural that they use other measures to cope with labor pain until they enter active labor and until it seems clear that positioning and activities are not putting a slow labor on track.

What do you tell your clients, students and patients about the impact on fetal positioning in labor and birth?  Will having this information change what you say?  Let us know in the comments section.

References

Anim-Somuah, M., Smyth, R. M., & Jones, L. (2011). Epidural versus non-epidural or no analgesia in labour. Cochrane Database of Systematic Reviews(12), CD000331.

Cheng, Y. W., Shaffer, B. L., & Caughey, A. B. (2006). Associated factors and outcomes of persistent occiput posterior position: A retrospective cohort study from 1976 to 2001. Journal of Maternal Fetal and Neonatal Medicine, 19(9), 563-568.

Fitzpatrick, M., McQuillan, K., & O’Herlihy, C. (2001). Influence of persistent occiput posterior position on delivery outcome. Obstetrics and Gynecology, 98(6), 1027-1031.

Lieberman, E., Davidson, K., Lee-Parritz, A., & Shearer, E. (2005). Changes in fetal position during labor and their association with epidural analgesia. Obstetrics and Gynecology, 105(5 Pt 1), 974-982.

Ponkey, S. E., Cohen, A. P., Heffner, L. J., & Lieberman, E. (2003). Persistent fetal occiput posterior position: obstetric outcomes. Obstetrics and Gynecology, 101(5 Pt 1), 915-920. 

Robinson, C. A., Macones, G. A., Roth, N. W., & Morgan, M. A. (1996). Does station of the fetal head at epidural placement affect the position of the fetal vertex at delivery? American Journal of Obstetrics and Gynecology, 175(4 Pt 1), 991-994.

Sizer, A. R., & Nirmal, D. M. (2000). Occipitoposterior position: associated factors and obstetric outcome in nulliparas. Obstetrics and Gynecology, 96(5 Pt 1), 749-752.

Thorp, J. A., Eckert, L. O., Ang, M. S., Johnston, D. A., Peaceman, A. M., & Parisi, V. M. (1991). Epidural analgesia and cesarean section for dystocia: risk factors in nulliparas. American Journal of Perinatology, 8(6), 402-410.

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Epidural Analgesia—a delicate dance between its positive role and unwanted side effects (Part Three)

March 4th, 2011 by avatar

[Editor’s Note: This is the last in a series of three posts by Dr. Michael Klein regarding the research behind risks, benefits and realities of epidural analgesia.  To read Dr. Klein’s first two posts, go here and here.]

Not all women are alike in labour and delivery:
Because the experience of labour pain, including severity, tolerance and contraction patterns, differs greatly among women, so does their ability to cope with the labour process.  In consequence, some women feel the need to receive epidural analgesia prior to the onset of active labour.  In some cases, the use of an early epidural will relax a woman enough to help her labour progress to the active phase and thereby lead to less subsequent medical interventions.  However, if used early without specific indications, a woman may find herself exposed to a larger range of interventions, including a caesarean birth.

Dealing with the reality of the labour ward:
Given this paradox and the severity of some of the side-effects of epidural analgesia, it is time to be honest about the full effects of this excellent technology: there is no such thing as a side-effect. There are only effects, some of which we like and some of which we don’t. When epidurals are used specifically to problem-solve, the risks of complications and other interventions are in fact reduced. When used routinely and mindlessly, epidural analgesia increases problems and adverse outcomes. Women need to be fully informed of this before agreeing to an epidural. Today, women are usually only informed of the direct consequences of epidural analgesia, such as a headache or even very rare neurological complications, but they are not often informed of the consequences that can occur if epidurals are given routinely or too early. They are rarely told about the potential deleterious effects of an epidural on the woman’s labour, nor the cascade of other interventions that might ensue. They are unlikely to be informed that an epidural will increase the demand on their nurse to pay greater attention to the technology and in consequence provide less hands-on support for the labouring woman. They are unlikely to be made aware of an epidural’s purported interference with the initial success of implementing breastfeeding following the baby’s birth.

Epidural analgesia is clearly an effective form of pain relief but it can also have less desirable consequences. Women need to be accurately and completely informed of their choices for pain relief in labour before they can provide their true consent. No matter how well intended, epidural analgesia increases the likelihood that women will have a variety of other interventions, especially if the epidural is given without specific medical indication. Women need to know that when epidural analgesia is given before the active phase of labour, it more than doubles the probability of a cesarean section.

The importance of timing and setting:
Women also need to be reassured that when epidural analgesia is given in the active phase of labour, it does not increase the cesarean section rate. This may motivate women to use other pain relief modalities and methods to help them, if possible, get to the active phase before requesting an epidural.

Readers of the literature also need to remember the importance of setting when reading about the research on epidural analgesia and any other interventions. All the statistics and outcomes that have been discussed here are in fact specific to the setting or environment from which the individual study or meta-analysis emanate. It is important to remember that adverse effects of epidural analgesia can be mitigated, especially if the setting generally limits the use of interventions. It appears, for example that in settings with low cesarean section rates (below 10%), even early epidurals do not increase the cesarean section rate,(21) but in more typical settings where cesarean section rates are higher than 20%, it does. This illustrates a general principle: For all studies, randomized or not, the reader needs to ask the question: do the caregivers in the studies practice the way that I do? If they do, the study may apply but if not, they may not.

The bottom line is that epidural analgesia has completely transformed birth. This massive change in the way that many women receive care in labour and birth has been based on a technique that, when used selectively and as a back-up tool or second line approach, is an important and valuable technique, among the many ways of assisting women with labour and birth. However, when used routinely as a first line agent, epidural analgesia can create problems that could have been avoided. Our Canadian National Study of the Attitudes and Beliefs of Maternity Care Providers has illuminated the very different ways that different disciplines view birth. (22) Most Canadian younger obstetricians (23)and women approaching their first birth (24) do not even know that epidural analgesia interferes with labour. The older generation of obstetricians knows that it does. They have experienced the changes related to epidural analgesia availability and usage during their many years in practice before and after the common use of epidural analgesia. It is time we told the truth about epidural analgesia – to colleagues and women – and engaged in a truly informed decision-making discussion with women about the optimal use of epidural analgesia.

References for this entire series of posts can be found here: References _ michael klein post

Post by:  Michael C. Klein, MD, CCFP, FAAP(Neonatal-Perinatal),FCFP, ABFP
Emeritus Professor of Family Practice and Pediatrics
University of British Columbia
Senior Scientist Emeritus
Centre Developmental Neuroscience and Child Health
Child and Family Research Institute
4500 Oak Street
Vancouver, V6H 3N1
Tel: 604-875-2000 ext 5078
Fax: 604-875-3569
Email:
mklein@interchange.ubc.ca

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