24h-payday

Archive

Posts Tagged ‘Occiput posterior’

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.

Childbirth Education, Epidural Analgesia, Evidence Based Medicine, Guest Posts, informed Consent, Medical Interventions, Pain Management, Research , , , , , , ,

Can We Prevent Persistent Occiput Posterior Babies?

January 29th, 2013 by avatar

Today, regular contributor Henci Goer, co-author of the recent book, Optimal Care in Childbirth; The Case for a Physiologic Approach, discusses a just published study on resolving the OP baby during labor through maternal positioning.  Does it matter what position the mother is in?  Can we do anything to help get that baby to turn?  Henci lets us know what the research says in today’s post. – Sharon Muza, Community Manager

_________________________

In OP position, the back (occiput) of the fetal head is towards the woman’s back (posterior). Sometimes called “sunny side up,” there is nothing sunny about it. Because the deflexed head presents a wider diameter to the cervix and pelvic opening, progress in dilation and descent tends to be slow with an OP baby, and if OP persists, it greatly increases the likelihood of cesarean or vaginal instrumental delivery and therefore all the ills that follow in their wake.

Does maternal positioning in labor prevent persistent OP?

This month, a study titled “Is maternal posturing during labor efficient in preventing persistent occiput posterior position? A randomized control trial” reported on the use of maternal positioning in labor to rotate OP babies to occiput anterior (OA). Investigators randomly allocated 220 laboring women with OP babies either to assume positions designed to facilitate rotation or to recline on their backs. The positions were devised based on computer modeling of the mechanics of the woman’s pelvis and fetal head according to degree of fetal descent. The position prescribed for station -5 to -3, i.e., 3-5 cm above the ischial spines, a pelvic landmark, had the woman on her knees supporting her head and chest on a yoga ball. At station -2 to 0, i.e., 2 cm above to the level of the ischial spines, she lay on her side on the same side as the fetal spine with the underneath leg bent, and at station > 0, i.e., below the ischial spines, she lay on her side on the same side as the fetal spine with the upper leg bent at a 90 degree angle and supported in an elevated position.

http://flic.kr/p/9Rs7mL

 

The good news is that regardless of group assignment, and despite virtually all women having an epidural (94-96%), 76-78% of the babies eventually rotated to OA. The bad news is that regardless of group assignment, 22-24% of the babies didn’t. As one would predict, 94-97% of women whose babies rotated to OA had spontaneous vaginal births compared with 3-6% of women with persistent OP babies. Because positioning failed to help, investigators concluded: “We believe that no posture should be imposed on women with OP position during labor” (p. e8). 

Leaving aside the connotations of “imposed,” does this disappointing result mean that maternal positioning in labor to correct OP should be abandoned? Maybe not.

Of the 15 women with the fetal head high enough to begin with position 1, no woman used all 3 positions because 100% of them rotated to OA before fetal descent dictated use of position 3. I calculated what percentage of women who began with position 2 or 3, in other words fetal head at -2 station or lower, achieved an OA baby and found it to be 75%—the same percentage as when nothing was done. What could explain this? One explanation is that a position with belly suspended is more efficacious regardless of fetal station, another is that positioning is more likely to succeed before the head engages in the pelvis, and, of course, it may be a combination of both.

Common sense suggests that the baby is better able to maneuver before the head engages in the pelvis. If so, it seem likely that rupturing membranes would contribute to persistent OP by depriving the fetus of the cushion of forewaters and dropping the head into the pelvis prematurely. Research backs this up. A literature search revealed a study, “Associated factors and outcomes of persistent occiput posterior position: A retrospective cohort study from 1976 to 2001“ finding that artificially ruptured membranes was an independent risk factor for persistent OP. Returning to the trial, all women had ruptured membranes because it was an inclusion factor. One wonders how much better maternal positioning might have worked had this not been the case, and an earlier trial offers a possible answer.

In the earlier trial, “Randomized control trial of hands-and-knees position for occipitoposterior position in labor,” half the women had intact membranes. Women in the intervention group assumed hands-and-knees for at least 30 minutes during an hour-long period while the control group could labor in any position other than one with a dependent belly. Twelve more women per 100 had an OA baby at delivery, a much bigger difference than the later trial. Before we get too excited, though, the difference did not achieve statistical significance, meaning results could have been due to chance. Still, this may have been because the population was too small (70 intervention-group women vs. 77 control-group women) to reliably detect a difference, but the trial has a bigger problem: fetal head position at delivery wasn’t recorded in 14% of the intervention group and 19% of the control group, which means we don’t know the real proportions of OA to OP between groups.

Take home: It looks like rupturing membranes may predispose to persistent OP and should be avoided for that reason. The jury is still out on whether a posture that suspends the belly is effective, but it is worth trying in any labor that is progressing slowly because it may help and doesn’t hurt.

Does maternal positioning in pregnancy prevent OP labors?

Some have proposed that by avoiding certain postures in late pregnancy, doing certain exercises, or both, women can shift the baby into an OA position and thereby avoid the difficulties of labor with an OP baby. A “randomized controlled trial of effect of hands and knees posturing on incidence of occiput posterior position at birth (2547 women) has tested that theory. Beginning in week 37, women in the intervention group were asked to assume hands-and-knees and do slow pelvic rocking for 10 minutes twice daily while women in the control group were asked to walk daily. Compliance was assessed through keeping a log. Identical percentages (8%) of the groups had an OP baby at delivery.

Why didn’t this work? The efficacy of positioning and exercise in pregnancy is predicated on the assumption that if the baby is OA at labor onset, it will stay that way. Unfortunately, that isn’t the case. A  study, “Changes in fetal position during labor and their association with epidural anesthesia,” examined the effect of epidural analgesia on persistent OP by performing sonograms on 1562 women at hospital admission, within an hour after epidural administration (or four hours after admission if no epidural had been administered), and after 8 cm dilation. A byproduct was the discovery that babies who were OA at admission rotated to OP as well as vice versa.

Take home: Prenatal positioning and exercises aimed at preventing OP in labor don’t work. Women should not be advised to do them because they may wrongly blame themselves for not practicing or not practicing enough should they end up with a difficult labor or an operative delivery due to persistent OP.

Do we have anything else?

Larry P Howell aafp.org/afp/2007/0601/p1671.html

We do have one ray of sunshine in the midst of this gloom. Three studies of manual rotation (near or after full dilation, the midwife or doctor uses fingers or a hand to turn the fetus to anterior) report high success rates and concomitant major reductions in cesarean rates, if not much effect on instrumental vaginal delivery rates. One study, “Manual rotation in occiput posterior or transverse positions: risk factors and consequences on the cesarean delivery rate,” comparing successful conversion to OA with failures reported an overall institutional success rate of 90% among 796 women. A “before and after” study, “Digital rotation from occipito-posterior to occipito-anterior decreases the need for cesarean section,” reported that before introducing the technique, among 30 women with an OP baby in second stage, 85% of the babies were still OP at delivery compared with 6% of 31 women treated with manual rotation. The cesarean rate was 23% in the “before” group versus 0% in the “after” group. The third study, “Manual rotation to reduce caesarean delivery in persistent occiput posterior or transverse position,” compared 731 women having manual rotation of an OP baby in second stage with 2527 women having expectant management. The success rate of manual rotation was 74% and the overall cesarean rate in treated women was 9% versus 42% in the expectantly managed group.

Manual rotation is confirmed as effective, but is it safe? This last study reported similar rates of acidemia and delivery injury in newborns. As for their mothers, investigators calculated that four manual rotations would prevent one cesarean. The study also found fewer anal sphincter injuries and cases of chorioamnionitis. The only disadvantage was that one more woman per hundred having manual rotation would have a cervical laceration.Take home: Birth attendants should be trained in performing manual rotation, and it should be routine practice in women reaching full dilation with an OP baby.

What has been your experience with the OP baby?  Is what you are teaching and telling mothers in line with the current research?  Will you change what you say now that you have this update?  Share your thoughts in the comment section. – SM

References and resources

Cheng, Y. W., 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 Medicine19(9), 563-568.

Desbriere R, Blanc J, Le Dû R, et al. Is maternal posturing during labor efficient in preventing persistent occiput posterior position? A randomized controlled trial. Am J Obstet Gynecol 2013;208:60.e1-8. PII: S0002-9378(12)02029-7 doi:10.1016/j.ajog.2012.10.882

Kariminia, A., Chamberlain, M. E., Keogh, J., & Shea, A. (2004). Randomised controlled trial of effect of hands and knees posturing on incidence of occiput posterior position at birth. bmj328(7438), 490.

Le Ray, C., Serres, P., Schmitz, T., Cabrol, D., & Goffinet, F. (2007). Manual rotation in occiput posterior or transverse positions: risk factors and consequences on the cesarean delivery rate. Obstetrics & Gynecology110(4), 873-879.

Lieberman, E., Davidson, K., Lee-Parritz, A., & Shearer, E. (2005). Changes in fetal position during labor and their association with epidural analgesia.Obstetrics & Gynecology105(5, Part 1), 974-982.

Reichman, O., Gdansky, E., Latinsky, B., Labi, S., & Samueloff, A. (2008). Digital rotation from occipito-posterior to occipito-anterior decreases the need for cesarean section. European Journal of Obstetrics & Gynecology and Reproductive Biology136(1), 25-28.

Shaffer, B. L., Cheng, Y. W., Vargas, J. E., & Caughey, A. B. (2011). Manual rotation to reduce caesarean delivery in persistent occiput posterior or transverse position. Journal of Maternal-Fetal and Neonatal Medicine24(1), 65-72.

Simkin, P. (2010). The fetal occiput posterior position: state of the science and a new perspective. Birth37(1), 61-71.

Stremler, R., Hodnett, E., Petryshen, P., Stevens, B., Weston, J., & Willan, A. R. (2005). Randomized Controlled Trial of Hands‐and‐Knees Positioning for Occipitoposterior Position in Labor. Birth32(4), 243-251.

Recommended resource: The fetal occiput posterior position: state of the science and a new perspective http://www.ncbi.nlm.nih.gov/pubmed?term=simkin%202010%20posterior by Penny Simkin.


 

Babies, Cesarean Birth, Epidural Analgesia, Guest Posts, Maternity Care, Medical Interventions, Research , , , , , , , ,