Sharon Muza asked me to do a blog post for Science & Sensibility expanding on a recent blog post I did for Childbirth U on the value, or lack thereof, of laboring down. Let me start by including that original post, and we'll go from there.

Medpage Today reports on a study contradicting the rationale for delayed pushing, or "laboring down," with an epidural. Analysis of the hospital records of 21,000 1^st-time mothers concluded that delayed pushing resulted in longer 2^nd-stage duration, longer active pushing phase, increased likelihood of cesarean and instrumental vaginal delivery, excessive postpartum bleeding, and more blood transfusions. By contrast, a recent Cochrane systematic review of randomized controlled trials (RCTs) (participants are allocated by chance to one form of treatment or the other) confirmed it. The review found that delayed pushing in women with epidurals results in longer 2^nd-stage duration but shorter active pushing phase, that it tends to increase spontaneous vaginal birth, and that it has no effect on the incidence of excessive postpartum bleeding or any other adverse maternal outcome measured in the trials. One study found that 2 more babies per 100 would experience low blood pH at birth, but pooled data failed to find an increased risk of admission to neonatal intensive care.

Which study has it right: the analysis of hospital records or the systematic review of RCTs?

To begin with, a RCT is the stronger design for this research question because RCTs set up a plan for how each group will be treated and then evaluate outcomes. In this case, women assigned to the "delayed" groups were told not to push unless they felt an uncontrollable urge, or the head was visible on the perineum (the block of tissue between the vagina and the anus), or until at least an hour (some trials prescribed longer delays) had passed after full dilation, and women in the "immediate" groups were directed to begin pushing at full dilation. A systematic review of RCTs is stronger yet because it pools data from multiple trials.

Investigators conducting the records analysis had to approximate a "delayed" versus "early" pushing group after the fact, which they did by defining "delayed pushing" as any labor in which pushing commenced 60 minutes or more after full dilation, "early pushing" as labors in which pushing began within 30 min after full dilation, and excluding women who began pushing between 31 and 59 minutes after full dilation.

This surrogate measure has several problems. The biggest is that women who develop a strong urge to push within the 1^st hour or whose baby descends to the perineum within that time and are therefore instructed to push wouldn't be counted in the "delayed" group. The review tells us this must happen fairly often. Average 2^nd stage duration in trials in 1^st-time mothers ranged from 1 hr 40 min to 3 hr 30 min, and it would likely take a while after beginning to push for 1^st-time mothers with epidurals to birth their babies. Another difficulty is that a definition based on timing alone assumes that the reasons for delay don't impact outcomes. The authors of the analysis acknowledge that this might not be the case, pointing out that pushing might be delayed in hopes of further descent or resolution of a malpositioned baby or because of maternal exhaustion. Similarly, while the RCTs evaluate outcomes from two groups distinguished by their differing treatment, the analysis chops a continuum of time arbitrarily into chunks and assumes an intentionality to those chunks. Furthermore, defining "early pushing" as within 30 minutes of full dilation isn't the same as "immediate pushing," as defined in the trials, which could also affect the validity of the analysis.

The analysis has yet another problem: all women in the RCTs have epidurals because the RCTs specifically evaluate a treatment for one of its harms: epidurals reduce spontaneous births because women don't push as effectively. The analysis, however, includes women who don't have an epidural.

The Take-Away

For these reasons, then, the vote goes to the systematic review. For women with epidurals, waiting to push until either a strong urge develops or the head descends to the perineum appears to do little or no harm and is likely to do some good. Women without epidurals, it should be added, don't need a policy. They should be aided in finding pushing positions other than reclining on the back and left to follow their bodies' instincts as to when and how to bear down.

Digging Deeper

We've established that the systematic review wins the debate, but it's still worthwhile to ask what factors might determine the relationship between second-stage duration and outcomes. Leaving aside the weaknesses of Yee's study design, it isn't biologically plausible that merely adding an hour or two more of contractions to the labor should significantly increase cesarean and instrumental deliveries, excessive postpartum bleeding, and blood transfusions.

A study by Cheng and colleagues (2014) sheds some light. They compared outcomes according to various definitions of prolonged second stage in 42,225 women giving birth between 1976 and 2008 at the University of California, San Francisco:

• ACOG's definition:
  • 1^st birth: > 120 min no epidural; > 180 min with epidural
  • subsequent birth: > 60 min no epidural; > 120 min with epidural
• ACOG's definition + 1 additional hour
  • 1^st birth: > 180 min no epidural; > 240 min with epidural
  • subsequent birth: > 120 min no epidural; > 180 min with epidural
• Population-defined definition based on the 95^th percentile threshold for 2^nd-stage duration
  • 1^st birth: > 197 min no epidural; > 336 min with epidural
  • subsequent birth: > 81 min no epidural; > 225 min with epidural

The investigators note that birth weight was stable over the time period, so that wouldn't have affected outcomes, and that immediate pushing was usual, which means that delayed pushing wasn't responsible for longer second-stage durations. I should add, too, that the hospital has a midwifery service and trains midwives as well as doctors. This means that conclusions may not be generalizable to institutions where only obstetricians practice because midwives tend to differ in practice style (Nijagal 2015).

The investigators found that neonatal outcomes were similar for second stages deemed "not prolonged" regardless of definition. They were also similar between "no prolonged second stage" and "prolonged second stage" within each definition for 5-min Apgar < 7, umbilical cord arterial pH < 7.0, meconium aspiration syndrome, sepsis, and intensive care admission. Incidence of birth trauma differed significantly, but absolute differences were small: 5 vs. 10 per 1000 using ACOG's definition, 5 vs. 12 per 1000 using ACOG's definition + 1 hr, and 5 vs. 16 per 1000 using the 95% threshold. Furthermore, "birth trauma" was a composite of cephalohematoma, head laceration, clavicular fracture, skull fracture, facial nerve injury, and brachial plexus injury. Undoubtedly traumatic injuries would most often be minor ones and ones that heal without long-term consequences, so while differences might be statistically significant, meaning unlikely to be due to chance, clinically significant differences are probably negligible.

Maternal outcomes showed somewhat more variability but still differed by only a few percentage points regardless of definition of second stage "not prolonged" for cesarean, instrumental vaginal delivery, anal sphincter injury, postpartum hemorrhage (not defined), chorioamnionitis, and endometritis. By contrast, major differences were found between "not prolonged" and "prolonged" second stages within each definition:

Note: The study's table is missing the cesarean rate with ACOG's definition + 1 hr, and the cesarean and instrumental delivery rates using ACOG's definition are identical, which suggests this may be an error; however, I was unable to contact a study author to obtain the cesarean rate or verify whether the ACOG definition's cesarean and instrumental delivery rates are correct.

• ACOG definition (34,263 women "not prolonged" vs. 8005 "prolonged"):
  • cesarean: 12% → 37%
  • instrumental delivery: 12% → 37%
  • anal sphincter injury: 7% → 16%
  • excessive bleeding: 6% → 15%
  • chorioamnionitis: 4% → 13 %
  • endometritis: 1% → 4%
• ACOG definition + 1 hr (38,345 women "not prolonged" vs. 3923 "prolonged"):
  • cesarean: [data missing from table]
  • instrumental delivery: 14% → 38%
  • anal tears: 8% → 17%
  • excessive bleeding: 7% → 17%
  • chorioamnionitis: 5% → 15%
  • endometritis: 1% → 4%
• 95^th percentile threshold (32,141 women "not prolonged" vs.1580 "prolonged"):
  • cesarean rate: 4% → 21%,
  • instrumental delivery: 17% → 31%,
  • anal tears: 9% → 15%,
  • excessive bleeding: 8% → 17%,
  • chorioamnionitis: 5% → 11%
  • endometritis: 2% → 4%

As you can see, the jumps between "not prolonged" and "prolonged"; are similar whichever definition is used. What changes markedly is the number of women labeled as having "prolonged second stage." With the ACOG definition, 8005 women fell into the prolonged second-stage category vs. 3923 women, or 4082 women fewer, in women given an additional hour. With the 95% threshold, only 1580 women fall in the "prolonged" category, or 6425 women fewer than using ACOG's definition. In other words, the prevalence of adverse outcomes depends not on second-stage duration per se but on when the birth attendant decides time's up. Obviously, at some point someone has to make the call that the baby isn't going to come out on its own, but that point isn't anywhere near where obstetricians commonly think it is.

The Bigger Issue

Cheng's study provides useful, evidence-based information on how long second stage can safely be, but that's only part of the puzzle. The bigger question is: "What care promotes second stages that safely end in spontaneous vaginal birth?" because absent reasons to curtail the labor, spontaneous vaginal birth produces the best outcomes for mother and child. We can do no better than to turn to Penny Simkin, who has much to say on this topic in women with and without epidurals. Except where otherwise sourced, the following recommendations come either from The Labor Progress Handbook (Simkin & Ancheta, 2011) or "Moving beyond the debate: a holistic approach to understanding and treating effects of neuraxial analgesia" (Simkin 2012).

• Help women avoid the need for an epidural by providing adequate supportive care and comfort measures and other strategies for coping with labor pain and by minimizing use of interventions that increase pain or inhibit labor progress. Epidurals increase instrumental deliveries (Anim-Somuah 2011), and they may increase cesarean deliveries (Bannister-Tyrell 2014), although this is controversial.
• Allow for a latent or resting phase at full dilation. Simkin & Ancheta (2011) explain that contractions may seem to slack off once the baby's head slips through the cervix until the uterine muscle fibers shorten enough to tighten up around the body. Directing women to push during this readjustment period may serve only to exhaust them to no effect.
• Time second stage from onset of the urge to push, rather than full dilation. This can decrease perception that second stage is prolonged, thereby reducing use of medical interventions. In women with epidurals, delay having them bear down until they develop an urge to push or the head becomes visible.
• Encourage women who don't have epidurals to push in the positions they find comfortable and effective. Avoid supine or semi-reclining positions. (Exception: Simkin & Ancheta [2011] note that pushing forcefully while lying supine with the knees drawn up may get a stubborn baby past the pubic bone when other measures have failed.) Suggest position changes if descent is slow. Pushing in a squatting or crouching position increases pelvic dimensions (Reitter 2014). Women with epidurals can push side-lying, and today's lighter epidurals make all-fours or even squatting possible with assistance.
• Have women without epidurals bear down according to their inner urges. Coach women with epidurals to push like women who are pushing spontaneously, i.e. bear down for 5-7 seconds, take 4-6 quick breaths and bear down again, repeating until the contraction wanes. The fetal monitor tracing can provide helpful biofeedback to women with epidurals.
• Explore and address emotional distress, which may arise from such factors as fear of injury or for the baby's wellbeing, embarrassment, realization of the immanence of the birth and therefore parenthood, or memories of previous sexual abuse.
• Try manual rotation to resolve persistent occiput posterior. It reduces cesarean delivery, anal sphincter injury, excessive postpartum bleeding, and chorioamnionitis (Le Ray 2007, Shaffer 2011).
• Refrain from presetting time limits. Judge individually based on how mother and baby are tolerating labor.

Breaking News

Citing Lemos (2015) and another systematic review and pointing out the weaknesses of Yee (2016), ACOG's February 2017 Committee Opinion, "Approaches to limit intervention during labor and birth," endorses laboring down:

Collectively, these data suggest that in the absence of an indication for expeditious delivery, women (particularly those who are nulliparous with epidural analgesia) may be offered a period of rest of 1-2 hours (unless the woman has an urge to bear down sooner) at the onset of the second stage of labor.

Photo credit "Lucile, bienvenue parmi nous" flickr photo by Raphael Goetter shared under a Creative Commons (BY) license

References

Childbirth U Post:

Lemos, A., Amorim, M. M., Dornelas de Andrade, A., de Souza, A. I., Cabral Filho, J. E., & Correia, J. B. (2015). Pushing/bearing down methods for the second stage of labour. Cochrane Database Syst Rev(10), CD009124.

Yee, L. M., Sandoval, G., Bailit, J., Reddy, U. M., Wapner, R. J., Varner, M. W., . . . Human Development Maternal-Fetal Medicine Units, N. (2016). Maternal and Neonatal Outcomes with Early Compared with Delayed Pushing Among Nulliparous Women. Obstetrics and Gynecology, 128(5), 1039-1047.

Science & Sensibility Post:

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

Bannister-Tyrrell, M., Ford, J. B., Morris, J. M., & Roberts, C. L. (2014). Epidural analgesia in labour and risk of caesarean delivery. Paediatric and Perinatal Epidemiology, 28(5), 400-411.

Cheng, Y. W., Shaffer, B. L., Nicholson, J. M., & Caughey, A. B. (2014). Second stage of labor and epidural use: a larger effect than previously suggested. Obstetrics and Gynecology, 123(3), 527-535.

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 and Gynecology, 110(4), 873-879.

Nijagal, M. A., Kuppermann, M., Nakagawa, S., & Cheng, Y. (2015). Two practice models in one labor and delivery unit: association with cesarean delivery rates. American Journal of Obstetrics and Gynecology, 212(4), 491 e491-498.

Reitter, A., Daviss, B. A., Bisits, A., Schollenberger, A., Vogl, T., Herrmann, E., . . . Zangos, S. (2014). Does pregnancy and/or shifting positions create more room in a woman's pelvis? American Journal of Obstetrics and Gynecology, 211(6), 662 e661-669.

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. J Matern Fetal Neonatal Med, 24(1), 65-72.

Simkin, P. (2012). Moving beyond the debate: a holistic approach to understanding and treating effects of neuraxial analgesia. Birth, 39(4), 327-332.

Simkin, P., & Ancheta, R. (2011). The Labor Progress Handbook (3rd ed.). West Sussex, UK: Wiley-Blackwell.

About Henci Goer

Henci Goer, award-winning medical writer and internationally known speaker, is an acknowledged expert on evidence-based maternity care. Her first book, Obstetric Myths Versus Research Realities, was a valued resource for childbirth professionals. Its successor, Optimal Care in Childbirth: The Case for a Physiologic Approach, won the American College of Nurse-Midwives "Best Book of the Year" award. Goer has also written The Thinking Woman's Guide to a Better Birth, which gives pregnant women access to the research evidence, as well as consumer education pamphlets and articles for trade, consumer, and academic periodicals; and she posts regularly on Lamaze International's Science & Sensibility. Goer is founder and director of Childbirth U, a website offering narrated slide lectures at modest cost to help pregnant women make informed decisions and obtain optimal care for themselves and their babies.

Tags