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.

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

According to Listening to Mothers II, a survey of U.S. women giving birth in 2005, 17% of women having vaginal birth reported a “health professional pressing down on her belly to help push the baby out” (Declercq 2006, p. 35). This is called fundal pressure, and 17% is fairly common, so I decided to look at its safety and effectiveness in the chapter I’m working on now for the new edition of Obstetric Myths Versus Research Realities. Here’s what I found out:

Fundal pressure can harm mothers. Three studies concluded that fundal pressure increased likelihood of anal sphincter injury. A small study comparing 34 women who had fundal pressure with 34 similar women who didn’t found that fundal pressure was a disaster for the anal sphincter when combined with midline episiotomy. Ten of 16 women—a whopping 63%—who had fundal pressure and episiotomy had an anal sphincter tear compared with only 1 woman of the 16—6%—who had episiotomy and no fundal pressure. A larger study of 845 women reported that fundal pressure increased the risk of anal sphincter injury 4.6-fold after adjusting for correlating factors. Rates in the overall population were 6% while rates with no fundal pressure were 3%, and rates with fundal pressure were 21%. A very large study of 238,500 women having spontaneous vaginal birth and 46,300 women having instrumental vaginal delivery found much smaller differences, but the addition of fundal pressure increased risk of anal sphincter injury with spontaneous birth (2.1% vs. 1.7%) and forceps delivery (5.2% vs. 4.7%), although, not, oddly enough, with vacuum extraction. Finally, a study looked at factors associated with painful intercourse 12 to 18 months after delivery. Investigators excluded women who had had anal sphincter tears. Even so, fundal pressure popped up as a problem. Among women experiencing painful intercourse, 35% had had fundal pressure compared with 13% of women not experiencing painful intercourse.

But we’re not done. Fundal pressure can harm babies too. A study of 13,700 vacuum extractions reported more brachial plexus injuries (a cluster of nerves serving the shoulder and arm) in babies when fundal pressure was used—2% versus 1%. Study authors theorized that fundal pressure may jam (the word they used was “impact”) the baby’s shoulder behind the pubic bone. So much for safety.

Still, every intervention has potential harms. The question is: “Does fundal pressure do sufficient good to counterbalance those harms?” Despite its fairly common use, until this year, we had no evidence that it did. Now we do, and it doesn’t. In a randomized controlled trial (women assigned by chance to one form of treatment or the other), investigators allocated healthy women with full-term, head-down babies and no epidural analgesia or oxytocin (Pitocin or “Pit”) infusion to have fundal pressure or not when they reached full dilation and felt an urge to push. (RCTs produce the strongest evidence because random assignment eliminates many sources of bias.) Second-stage duration rates were similar in the group overall as well as among first-time mothers and among women with prior births. Ominously, umbilical cord oxygen levels at birth were lower in the fundal pressure group and carbon dioxide levels were higher. All newborns were in good condition at birth, but these were healthy pregnancies, and the same might not be true for babies already having some difficulty. So much for efficacy.

I could speculate on why the practice has persisted and continues to persist in the absence of any evidence to support it—in fact, I will in the book—but the take-home pay here is if progress is slow in second stage, women would be much better off trying an upright position, or better yet, preventing the slow progress by staying off her back in the first place and choosing a provider who practices patience rather than imposing time limits on second stage. Most women can get upright even with an epidural and confined to bed. Modern epidurals can relieve pain while still leaving sufficient feeling and muscle strength in the legs, for example, to rest on hands and knees between contractions and push back onto heels during contractions, or to kneel upright using a stack of pillows or a stability ball (A.K.A. “birth ball”) for support, or to sit between contractions and use the help of labor companions or a squatting bar to pull into a squat during contractions. Women with weak contractions would also be better off using breast stimulation or having I.V. oxytocin to bring strength up to par before resorting to more aggressive means of getting the baby born. And if push does come to pull, instrumental vaginal delivery isn’t entirely harmless, but at least it’s effective. Fundal pressure is neither. The wise woman whose care provider wants to press on the top of her belly either alone or in conjunction with instrumental delivery, will, in the words of a famous campaign, “just say, ‘No.’”’

Click on the extended post to see the references.

Read more…

Henci Goer do no harm, research for advocacy epidurals, episiotomy, fundal pressure, pelvic floor, second stage

Reality TV fans (not me) and readers of the Celebrity Baby Blog (OK, that’s me) may have heard that Kendra Wilkinson of The Girls Next Door “fame” is expecting her first baby this winter.  In addition to the news that Kendra’s ex, Hugh Hefner, will be the baby’s Godfather (ick!), CBB readers were treated to some early news on Kendra’s wishes for her labor and birth.

“I’m getting an epidural, everything they can give me,” she reports. “That’s the one thing I’m nervous about the most. Everything else is so fun, but I have visions of my vagina tearing, and that sucks.”

A red flag popped up when I read this. An epidural is about the last thing I would recommend to someone who was nervous about her vagina tearing. Why? Because if there is one thing that no one disputes about epidurals, it is that they increase the need for forceps- or vacuum-assisted delivery. And instrumental vaginal birth is not good for vaginas.

It seems to me Kendra wants her cake and to eat it to. Either that, or she has very unrealistic expectations of what an epidural can and cannot achieve. But Kendra shares a concern with many women (albeit, whose careers may be less wrapped up in their sexual and reproductive organs) who want to preserve their genital integrity in birth. With this in mind, I thought I’d take this opportunity to share some tips, supported by scientific research and a little common sense, on how to protect against genital tract injury in childbirth.

1. Choose a provider with a low episiotomy rate – under 5%. Research confirms that your provider’s episiotomy rate is the single strongest predictor of whether you will have one. Episiotomies, by definition, cause injury to the tissue of the vagina and perineum. They also predispose women to severe injuries that involve the anal sphincter. A large body of research tells us that midwives use episiotomy less than doctors do, but there is much variation in episiotomy use across midwives, too, so it’s best to ask.
2. Choose a provider who rarely uses a vacuum or forceps. In studies of first-time mothers, the rate of instrumental vaginal delivery in women without epidurals has been reported to range from 4-60%. This huge variation can only be explained by factors that have nothing to do with women and babies (arbitrary time limits, the provider’s attitudes, etc.). If instrumental assistance is needed to get the baby born safely, choose a vacuum rather than forceps.
3. Give birth off your back and follow your own pushing urges. Studies show that giving birth on your back and “purple pushing” can increase the chance of an instrumental vaginal birth, an episiotomy, or both. Letting someone push on your abdomen while you give birth (fundal pressure) increases the chance that a tear will extend into the anal sphincter muscle.
4. Avoid continuous electronic fetal monitoring unless there is a good medical reason for it. It increases the chance of instrumental vaginal birth.
5. And again, plan to give birth without an epidural because of the much higher risk of instrumental vaginal delivery that comes along with an epidural. If you do have an epidural, wait for an hour or longer after you are fully dilated to begin pushing, unless a strong urge develops sooner. This practice of “laboring down” decreases the chance of instrumental vaginal delivery and reduces the likelihood and severity of lacerations. It’s also safer for babies.

I’ve said it before and I’ll say it again: epidurals may make coping with labor pain easier, but they often make labor itself much more difficult. The urge to push may be decreased, delayed, or absent. And epidurals increase the chance that a baby will settle into the pelvis facing toward the mother’s front or side (occiput posterior or transverse), which makes it much harder to push the baby out. If a baby gets stuck in this position, a vaginal birth is very difficult to achieve and if the baby does come out vaginally, a severe laceration is likely. Women who want epidurals must be told of these trade-offs, and women who want to optimize their chance of a safe vaginal birth with minimal or no tearing must be given the full range of pain relief options and care that maximizes comfort to reduce the need for epidurals.

As for what women or providers can do proactively to avoid genital tract trauma, the research here has come up rather short. Whether the provider has her hands on the perineum or not, whether lubricants or warm compresses are used, and whether the woman performs perineal massage prenatally all have minimal if any effect. One approach that was found to be statistically associated with a reduction in trauma is birthing the baby’s head between contractions. A team of midwifery researchers in New Mexico reported this finding and concluded the following:

To deliver the fetal head between uterine contractions requires a joint effort by the mother and her clinician to achieve a slow and controlled expulsion of the baby, requiring patience and effective communication from the clinician. In these data, a calm and unrushed approach to vaginal birth improved the health of new mothers by lowering overall trauma rates and reducing the need for suturing. (Albers 2006, p. 99)

This reinforces points #1 and #2 above: Choose your provider wisely.

Still not convinced? Or think that a c-section is the answer? Childbirth educator, Mamarama, gives the straight talk on that myth. Hat-tip to A Much Better Blog for passing on the link.

Click on the extended post to see a bibliography.  Read more…

Amy Romano Uncategorized celebrities, electronic fetal monitoring, epidurals, episiotomy, interventions, pelvic floor, practice variation