Science & Sensibility

The levator ani is a muscle, not a clinical outcome.

Ok, ok, I’ve heard from enough of you about the study purportedly showing that epidurals protect the pelvic floor, I suppose it’s time to write up what I think about it.  First, a little about the study from the (overzealous) journal press release. I couldn’t resist doing a little bit of [line editing] on it:

Researchers from Australia undertook a prospective study of 488 women undergoing their first pregnancy between May 2005 and February 2008. The object of the study was [to determine predictors of delivery mode, but since they had enrolled all of those pregnant women they designed some other studies, too. In one, the researchers invited those 488 women to return for follow up at 3-4 months and retrospectively analyzed data on the 367 women who did] to determine if there are any risk factors during birth which may result in levator trauma including macrotrauma (large scale avulsion – tearing) and microtrauma (damage to the muscle tissues such as irreversible overdistention of the pelvic floor opening). Researchers believed that the findings from their study may help modify obstetric practice to help prevent levator injury…

No levator avulsion was recorded in the women who had a caesarean section. Levator avulsion was diagnosed in 13% of women who had a vaginal birth (9% of whom had had a vacuum delivery and 35% of whom had had a forceps delivery). Researchers found that forceps delivery was associated with a three to four-fold increase in levator avulsion. [They excluded the 13% of vaginal births in which levator avulsion was diagnosed and evaluated the rest of the women for "microtrauma". We put "microtrauma" in quotes because no one has ever defined or determined the prevalence of this "condition". The researchers invented it themselves! But anyway,...] Postbirth assessment showed that the longer the 2nd stage of labour, the higher the likelihood of microtrauma. Women who had an intrapartum epidural were found to have had a lower incidence of microtrauma. The researchers suggest that epidurals, because they relax the muscles through paralysis, may be beneficial in preventing levator trauma.

There are multiple problems with the press release and, for that matter, with the study itself. Christine Kent at Whole Woman Village Post does a nice job of reviewing some of them, including the fact that one of the study authors receives money from incontinence surgical device companies and ultrasound companies. But I’d like to focus on the use of “levator microtrauma” as the outcome reported.

Levator microtrauma is an example of a surrogate outcome (sometimes referred to as a surrogate endpoint). As defined by Temple (1995):

A surrogate endpoint of a clinical trial is a laboratory measurement or a physical sign used as a substitute for a clinically meaningful endpoint that measures directly how a patient feels, functions or survives. Changes induced by a therapy on a surrogate endpoint are expected to reflect changes in a clinically meaningful endpoint. [emphasis mine]

But as D’Agostino (2000) argues, some surrogate outcomes are extremely poor predictors of actual outcomes, and changing clinical practice based on studies that report only surrogate outcomes can be a major threat to patient safety if the therapy introduces other risks. So the questions we should ask ourselves when we see a study reporting a surrogate outcome are:

• is the surrogate outcome a good predictor of a clinically important outcome (i.e., “how a patient feels, functions or survives”)?
• does the treatment pose any excess risks over other alternatives to achieving that clinically important outcome?

In the case of “levator microtrauma,” there is absolutely no data whatsoever linking the author’s definition of microtrauma to pelvic organ prolapse or other important pelvic floor problems such as incontinence or sexual dysfunction. The aforementioned corporate-sponsored researcher showed in an earlier study that macrotrauma (aka levator avulsion) is an appropriate surrogate for pelvic organ prolapse, but remember that epidurals were not associated with macrotrauma in this study. Forceps deliveries were – and what’s the major modifiable risk factor for forceps delivery?  Epidurals!

But let’s say that microtrauma does lead to pelvic floor problems and that, therefore, epidural analgesia in labor may be a strategy for preventing those pelvic floor problems.  Is encouraging epidural analgesia in a woman who might otherwise forgo it the best strategy for preventing pelvic floor problems?  Maybe doing away with coached pushing, fundal pressure, episiotomy, and supine positioning might be the better strategy. Maybe postpartum exercises can help reverse changes associated with pregnancy and vaginal birth so they don’t turn into symptomatic pelvic floor problems.

Like other studies that report surrogate outcomes, this study is not useless.  It provides some data that can help us understand how epidurals affect pelvic floor muscle tone and strength and alter the process of vaginal birth, and I’ll be the first to say that we need more research in those areas. In other words, these data on a novel surrogate outcome can help us design more studies, not guide patient care.

Anyone who has even a basic understanding of clinical research should recognize that we need much more data before we can say that epidurals may help prevent future pelvic floor prolapse.  Oh wait, the editor-in-chief of a major international obstetric journal just said exactly that! In the headline of a major press release!

*headdesk*

Reference:

Temple RJ. A regulatory authority’s opinion about surrogate endpoints. Clinical Measurement in Drug Evaluation. Edited by Nimmo WS, Tucker GT. New York: Wiley; 1995.

Uncategorized bias, epidurals, interventions, pelvic floor, safety, surrogate outcome

Iatrogenic (adjective): induced in a patient by a health care provider’s activity, manner, or therapy. An iatrogenic disorder is caused by medical personnel or procedures or develops through exposure to a health care facility.

Iatrogenic norm: a defined range of normal values for a biological process that, rather than describing actual normal physiology, instead measures the consequences of a health care provider’s beliefs, actions, or therapies or the effects of exposure to a health care facility.

Clinicians today base labor management on norms for cervical dilation rate in active phase labor (assumed to begin somewhere between 3 and 5 cm dilation in women contracting regularly) derived from research conducted decades ago by Friedman and colleagues (the famous “Friedman curve”). According to this research, in first-time mothers, the slowest 10%, an arbitrary cutoff for abnormally slow progress, dilate at a rate of 1.2 cm per hour or less. This norm has been enshrined in the “action lines” of the graphs of “dilation versus time” routinely used to manage labor. The “action” taken when women fail to progress at this minimal rate is administration of intravenous oxytocin to strengthen contractions, and such women are at high risk for cesarean surgery for labor dystocia. If this criterion is overly stringent, women with normally progressing labors will be subject to potentially harmful treatment and surgical delivery unnecessarily.

Concern over this possibility led a group of investigators to conduct a systematic review of studies analyzing active labor duration, progress rate, or both in active first-stage labor in first-time mothers, and the lead author, Jeremy Neal, presented the results at the recent Normal Labour & Birth International Research Conference. Neal began his talk with a look at the body of evidence that gave rise to this concern. I won’t bore you with the details, but suffice it to say that studies using Friedman’s norms for progress diagnose anywhere from one-quarter to one-half or more of first-time moms as requiring treatment for abnormally slow progress. If progress is abnormal in that many women, then something is wrong with the definition of normal, or, as Neal put it:

Either many nulliparous women are admitted prior to progressive (active) labor yet held to dilation expectations of “active‟ labor and/or common expectations of active labor dilation rates (e.g. 1 cm/hr) are unrealistically fast.

The group’s review pooled data from 25 studies encompassing thousands of low-risk first-time mothers with spontaneous labor onset at 36 weeks of pregnancy or more. It found that contrary to Friedman, 1.2 cm was actually the mean rate of dilation, not the rate in the slowest 10%, and the limit for the threshold of slowest acceptable progress rate fell at 0.6 cm, half that rate. (This, by the way, is not a physiologic norm because studies included women with epidurals and labor augmentation, and since all data came from hospital studies, laboring women would have been subject to policies that could affect progress rate such as confinement to bed. That being said, the review found that epidural use did not change results.)

Neal then added that active labor is assumed to progress at a constant rate, but some data suggest that rate of progress may be slower at the beginning of active phase and accelerate as it continues. In other words, the action “line” is another iatrogenic norm because it should be an action “curve.” If this is true, using an action line would put even more women progressing normally in early active phase in jeopardy of the “dystocia” diagnosis and all that follows.

Neal concluded with: “Revision of existing ‘active’ labor expectations and/or revision of criteria used to prospectively identify active labor onset is warranted and such efforts should supersede efforts to ‘change’ labor to fit existing expectations.” “From his mouth to God’s ears,” as they say—or at least to the ears of obstetricians.

Nevertheless, while revising norms to match reality would take a big step in the right direction, I would argue it doesn’t go nearly far enough because it still sticks us with the assumption that active first-stage dilation progresses smoothly. Anyone who has spent time with laboring women knows that this is often not the case. Neat graphical lines (or curves) come from averaging many highly variable individual labors, so the very expectation of how labors progress, at whatever pace, is itself an iatrogenic norm.

Moreover, the published review points out that both the old and the proposed new threshold for “abnormal” are statistically derived (e.g. two standard deviations beyond the mean). No study links a cut point for “abnormally slow” with an increase in perinatal morbidity, but averting adverse outcomes should form the basis for intervening medically because of the risks of intervention. In fact, even if a study tried to establish an outcome-based threshold, it would be hard to determine whether the increase was due to labor duration per se or to the interventions used to treat slow labor. So we have yet another iatrogenic norm, this one having to do with a definition of “abnormal” with no clinical significance.

In short, forcing labor to conform to artificial, arbitrary guidelines does more harm than good. A simplistic cookbook approach to the knotty problem of labor dystocia has obvious appeal, but what is truly needed to achieve the best outcomes with the least use of medical intervention is thoughtful evaluation, individualized care, and above all, patience so long as mother and fetus are tolerating labor. Labor graphs and action lines do no more than exemplify H. L. Mencken’s truism, “For every complex problem there is a solution that is simple, neat—and wrong.”

Uncategorized labor progress, Normal Labour & Birth Conference, systematic review

I know when I set out to change something about my health, a few things make the process much easier and, for that matter, more likely to yield the benefits I’m after. I’m particularly aware of this these days as I’ve recently (successfully!) changed some health habits that put me at risk for heart disease, which, with my family history, really needed to be addressed. In making these changes, I realized that my success reflected the body of literature that tells us that change is easiest and more likely to stick when you:

• know what you need to change and why
• start with small, feasible objectives that move you toward a larger goal
• have support, especially from others who are also trying to change or who have done so successfully already
• track your progress and adjust your approach as needed
• measure and celebrate your results

Large organizations, such as hospitals or healthcare systems, are capable of change, too, and there’s another body of literature on how effective organizational changes unfold. But knowledge of the problem, peer support, and tracking and measuring against feasible objectives are no less important. That’s why I’m excited about the Institute for Healthcare Improvement (IHI) Perinatal Improvement Community. Any hospital interested in improving perinatal care and outcomes can enroll in the community and take advantage of their measurement tools as well as support from IHI experts and other participating hospitals. IHI organizes its improvement efforts around “bundles” so that hospitals can work toward change in one focus area at a time, with the overarching goals of reducing harm through better communication and teamwork, patient-centered care, and less unwarranted variation in care practices. Hospitals that participated in the first round of the Perinatal Improvement Community worked on safe use of induction and augmentation, including eliminating elective inductions prior to 39 weeks. The next round of participation will focus on Second Stage Safety, and hospitals must enroll by next Wednesday, September 1. Check out IHI’s web site to learn about the results of participating hospitals’ improvement efforts and to find out how your hospital can enroll.

Uncategorized

The (in)famous Wax home birth meta-analysis hit the scene over a month ago. But the buzz doesn’t seem to be dying down. In the weeks since the original pre-publication and press release, editors at The Lancet and BMJ have both weighed in, and there’s a steady stream of media attention. While all of the media have dutifully quoted midwives in leadership positions saying the meta-analysis is flawed (an assessment with which I agree), I still keep coming back to the question I asked in my earlier post – did we need a meta-analysis to establish the neonatal outcomes of planned home birth? We had, after all, a very large, methodologically rigorous study on home birth safety involving over a half million women that was published less than 2 years ago. Won’t that suffice?

I had a chance to interview two of the researchers who conducted that study when I was in Vancouver for the Normal Labour & Birth International Research Conference. Simone Buitendijk, MD, is Professor of Maternal and Child Health and Midwifery Studies at the Academic Medical Center of Amsterstam and heads up the Child Health Programme at the Netherlands Organisation for Applied Scientific Research. Ank de Jonge, the study’s lead author, is a practicing midwife with a PhD in public health who works at the Midwifery Science section within the EMGO Institute for Health and Care Research at VU University Medical Center in Amsterdam. I gained some new insights from them about their research and the Wax meta-analysis. Based on those interviews, and despite having written about the meta-analysis twice already, I thought it was time to ask anew: which is the “better” evidence for determining neonatal outcomes of planned home birth: the de Jonge cohort study or the Wax meta-analysis? Let’s have a look at some objective criteria and see how each study measures up.

Study size (home birth group):

• Wax: 9,811
• de Jonge: 321,307

That’s right, the Dutch neonatal mortality analysis is 33 times the size of the neonatal mortality meta-analysis. And believe it or not, this was BRAND NEW news to me that I didn’t realize until I spoke to de Jonge and Buitendijk. Although I had access to the full-text of the Wax meta-analysis and in fact looked critically at it (heck, I blogged about it!), I completely missed the fact that while the de Jonge study was “included” in the meta-analysis, it was excluded from the analysis of neonatal mortality, which was the major finding given so much attention by the media.  On the one hand, I’m pretty embarrassed to have made such a major error. On the other hand, it just underscores how misleading it can be for professionals or lay people to read headlines about a meta-analysis of “hundreds of thousands” of births finding triple the neonatal death rate.  Wax’s neonatal death data don’t come from hundreds of thousands of births at all. Not by a long shot.

Mechanism to ensure data were from planned home births:

• Wax: mechanism varies across the included studies. In Pang et al., which contributed 63% of the home birth data and accounted for 12 of the 18 neonatal deaths in normally formed newborns, researchers relied on birth certificate data that did not differentiate between planned and unplanned home births, and assumed that any birth certificate for a baby born at home at or beyond 34 weeks, signed by a midwife, nurse, or doctor was a planned home birth, a method that has not been scientifically validated and has been widely criticized. Unplanned home births are riskier than planned home births with qualified attendants.
• de Jonge: midwives routinely record the planned place of birth in a national perinatal database that covers 99% of births and is linked to another database of neonatal deaths by a validated method. Planned place of birth was unknown for 8.5% of the population, and the outcomes of this group were analyzed separately and reported.

Definition of neonatal death:

• Wax: death of a live-born infant between 0 and 28 days
• de Jonge: death of a live-born infant between 0 and 7 days (the World Health Organization definition of early neonatal death)

The appropriate definition of neonatal death has been a major bone of contention in the comments on this and other blogs that criticized the Wax meta-analysis.  Both 0-28 days (neonatal death) and 0-7 days (early neonatal death) are accepted definitions. Proponents of using early neonatal death argue that it is more sensitive to events occurring around the time of birth, such as hypoxic injury resulting from inadequate fetal monitoring or a sudden emergency like a cord prolapse or placental abruption. Indeed, some of the late (8-28 days) neonatal deaths reported in Wax resulted from sudden infant death syndrome, a condition that has nothing to do with planned place of birth. On the other hand, proponents of using 0-28 day mortality point out that some babies experiencing severe hypoxic injury in labor or birth may be kept alive for many days in a modern neonatal intensive care unit.  Their deaths should be counted as birth-related even if they don’t die as soon after birth.

Regardless of which is the more appropriate measure, I was shocked by something de Jonge and Buitendijk revealed in their interview. Wax never contacted them to ask for their 8-28 day mortality data. It is standard practice among researchers who conduct meta-analyses to contact the authors of the original papers to obtain unpublished data, clarify methodologies, or ask for data in a compatible format. One would think that if Wax was truly interested in whether planned home birth caused neonatal death up to 28 days, he would be very motivated to get his hands on the Dutch data set. And while de Jonge and Buitendijk told me that those data are not as complete as the early neonatal death data (because some pediatricians don’t reliably enter their patients’ data), they do in fact have the data up to 28 days and would have supplied it to Wax had he asked. Instead, they have done the analysis themselves and submitted it for peer review.  (Therefore, we’ll have to wait for the results.)

What were the characteristics of the population?

• Wax – no requirements for home birth eligibility were defined for inclusion in the meta-analysis. Individual studies included in the meta-analysis varied in their mechanisms for determining eligibility. As noted above, the largest study that contributed the majority of neonatal deaths relied on birth certificates. Women with any of 18 medical conditions documented on the baby’s birth certificate were excluded. Neither the study authors nor Wax and colleagues comment on whether this is a reliable method for defining “low-risk”. (As someone who routinely completed birth certificates when I was practicing, my guess is that it isn’t.)
• de Jonge – National guidelines (”Obstetric Indication List“) define who is eligible for primary midwifery care and home birth. These conservative guidelines ensure that the population of women having planned home births are healthy and at very low risk of complications.

The Dutch study has been criticized because it is, well, Dutch – midwifery and home birth in the Netherlands are highly regulated and integrated into the system, and there are clear eligibility guidelines. The same isn’t true of the United States, so we can’t generalize the results here or elsewhere where home birth is marginalized (e.g., Australia). What the Dutch study gives us, though, is a clear model to emulate in order to make sure home birth is as safe as it can be – regulate midwifery, provide continuity of care for women who need to be referred, and make sure only low-risk women are having home births. Instead of acknowledging this and moving forward to optimize safety, Wax and colleagues chose to mash together data from five different countries and four different decades with no attention paid to which women were and were not eligible and spit out an authoritative answer to the question, “Is home birth safe?” “Is home birth safe?” is a bogus question to which there is no answer. Context, training, system integration, and perhaps above all else the characteristics of the population matter. Any study worth its salt will describe these factors in as robust detail as is feasible. Combining and meta-analyzing data from dissimilar contexts may make sense in other areas of health care, but when context is everything, what’s there to gain?

A note about comments: please keep it civil and on point. I’m OK with debate, discussion, and disagreement. Name-calling, personal attacks, and other degrading commentary will be deleted or edited.

Uncategorized home birth, media, meta-analysis, Normal Labour & Birth Conference, safety

The blog has been quiet for longer than usual. I had a great family vacation at the beginning of the month and came back to deadlines. I’ve got a pile of blog posts half-written and some good stuff in the pipeline, but I thought I’d share a few papers of interest to childbirth educators in the meantime. I don’t have the time to give these the full critical treatment, but I knew my CBE readers (and maybe others) would want to know about them.

1. The current issue of the Journal of Obstetric, Gynecologic, and Neonatal Nursing (JOGNN) has several articles on disaster preparedness efforts for childbearing women and newborns. I was happy to see this since I wrote recently that this topic has gotten too little attention. One of the articles, titled Targeting Prenatal Emergency Preparedness Through Childbirth Education, suggests including disaster preparedness in childbirth education offerings,  proposes a topical outline for curriculum development, and reviews relevant literature on disaster planning, evacuation and public sheltering, and the mental health consequences of disasters for childbearing women.

2. In the journal, Medical Decision Making, researchers from the Cochrane Collaboration present the outcomes of qualitative research aimed at improving consumers’ comprehension of “plain language summaries” of Cochrane Systematic Reviews. The results, as presented in the abstract, reveal that consumers have very limited knowledge of what a systematic review is and how to interpret findings, a problem of major importance to perinatal educators who wish to convey evidence from systematic reviews.

Participants preferred results presented as words, supplemented by numbers in a table. There was a lack of understanding regarding the difference between a review and an individual study, that the effect is rarely an exact number, that evidence can be of low or high quality, and that level of quality is a separate issue from intervention effect…Confidence intervals were largely ignored or misunderstood. Our attempts to explain them were only partially successful. Text modifiers (’probably,’ ‘may’) to convey different levels of quality were only partially understood, whereas symbols with explanations were more helpful. Participants often understood individual information elements about effect size and quality of these results, but did not always actively merge these elements.

As a result of these findings, the Cochrane Collaboration is currently evaluating a new format for Plain Language Summaries.

3. An article in press in the journal Midwifery reports findings from a qualitative study of 11 first-time fathers’ expectations and experiences of being present during labor and birth. Two of the fathers’ partners gave birth by elective cesarean section, two had emergency cesareans, three had  instrumental births and four had a spontaneous vaginal births. All of the couples had taken hospital antenatal classes. Most of the fathers reported in prenatal and postnatal interviews:

• feeling disconnected from their partners during pregnancy and labor
• feeling on the periphery of events during labor
• feeling ill prepared for and alienated from decision-making, and
• “becoming a father” and reconnecting with the experience and their partners at the moment of birth.

The authors concluded,

Birth is the moment that fathers ascribe as the beginning of fatherhood. However, through their lack of knowledge and perceived control, they struggle to find a role there.

4. And finally, my article, Social Media, Power, and the Future of VBAC, co-authored with Hilary Gerber and Desirre Andrews, is out in the current issue of the Journal of Perinatal Education and it’s FREE! The article reviews the contemporary consumer movement for improved access to VBAC and explores the role of social media in enabling access to evidence-based information and peer support. It’s my contribution to the “Looking Back/Looking Forward” issue of the Journal, which marks and celebrates Lamaze’s 50th anniversary. I hope to feature much more from this important issue of the Journal, but in the meantime members can access the full issue for free.

Uncategorized childbirth education, fathers, systematic review, VBAC