Science & Sensibility

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Occasional Science & Sensibility contributor Rebecca Dekker of Evidence Based Birth has spent the last month writing a blog article about Group B Strep and it is finally here! In her painstaking but clear review of the evidence on GBS in pregnancy, Rebecca came to the conclusion that universal screening and treatment for GBS is more effective than treating with antibiotics based on risk factors alone. She also found that although “probiotics, chlorhexadine, and garlic have the potential to reduce vaginal and newborn colonization with GBS, we do not have evidence yet to show that these strategies can prevent early GBS infections, since GBS infection usually occurs when GBS gains access to the amniotic fluid and gets into the fetus’s lungs during labor.”

To read Rebecca’s just released article, Group B Strep in Pregnancy: Evidence for Antibiotics and Alternatives in its entirety, click here.

Today, Rebecca joins us on Science & Sensibility to talk about her latest addition to Evidence Based Birth.

Sharon Muza: What inspired you to write this article?

Rebecca Dekker: I received more requests to write about Group B strep than any other topic! Over the past few months, I had weekly, sometimes daily emails and Facebook messages from women—all asking me to provide them with evidence about antibiotics, hibiclens, or garlic for preventing GBS infections. After about the 50th request, I figured I better set aside my other plans and focus on this topic, because it was clearly weighing heavily on many women’s minds! 

SM: What was the most difficult thing about writing this article?

RD: Probably the most difficult thing was sorting through the stacks and stacks of research articles that have been published about Group B strep in pregnancy. This was one of the reasons it took me almost a year of blogging before I decided to dive into group B strep. I knew it would be a monumental task. And it was. But I was fortunate enough to have an expert in GBS who helped point me to the most important or “landmark” studies.

SM: Who was this expert?

RD: I met Dr. Jessica Illuzzi via email earlier this year. She and I had corresponded about a different blog article, and at that time I found her to be incredibly helpful. I knew that in addition to being an OB, Dr. Illuzzi was a research expert in GBS. So I asked her if she would review my article for me. To be honest, I could not have written this article without her guidance. She read my first draft and basically told me that I needed to go back to the drawing board. She encouraged me to dig deeper into the evidence so that I would really understand it. Whenever I had questions about something, she sent me research articles that immediately answered my question. In the end, I knew the article was ready when she said it was a great summary of the state of the science of GBS. 

I was also lucky enough to have 2 other GBS experts give me feedback on the article—a GBS researcher and a microbiologist. And then I have several physicians who faithfully review all of my articles and give great suggestions. I am very grateful to all of them as well!

SM: I know that you usually begin your articles with an exploration of your own biases, in order to tease the bias out of your writing. Did you have any pre-existing biases about GBS? 

RD: To be honest, I actually had no biases up front. I was fortunate to always test negative for GBS myself, and so I never had to struggle with this issue before. I was pretty open-minded to the entire issue. I was open-minded to antibiotics. I was open-minded to hibiclens or other alternatives. I had no personal agenda. I simply wanted to get to the facts. Hopefully this lack of bias will shine through and help people respect the article even more.

 SM: What surprised you most as you wrote this article?

RD: One of the things that surprised me was how people have such different reactions when they read the evidence about GBS. I had several friends preview the article for me. Some of them instantly said, “Oh yeah, that sounds like a really high risk. I’d definitely take the antibiotics to prevent an infection in my newborn.” Others would say, “Really? That’s all? That’s not a very high risk at all. I wouldn’t take antibiotics for that level of risk.” This is a great example of how everyone perceives risk differently. But at least in this article I have been able to put some evidence-based facts out there. Let people interpret the risks as they may. I only ask that they talk with their health care provider before making any decisions!!

 SM: What do you think is the future of GBS evidence?

RD: Ten years from now I am guessing that I could write a very different article. I would like to think that by then we may have a vaccine on the horizon that could prevent both early GBS infections and GBS-related preterm birth. It would also be nice if the rapid test was affordable and widely available by then. I would also LOVE to see some solid research evidence on the use of probiotics for decreasing GBS colonization rates in pregnant women. As far as I know, probiotics for decreasing GBS hasn’t been studied yet in pregnant women, and I think it deserves further inquiry.  

SM:What makes your blog article about GBS different than all the other blog articles out there on this topic?

Rebecca Dekker

RD: I purposefully didn’t look at any of the other GBS blog articles out there until I finished my article. Yesterday, I read through a variety of blog articles (there are a lot!). Most of them were about 90-95% accurate in their facts. A couple of them had serious errors (in particular, I found one blog article that had inaccurate information about hibiclens). Most didn’t list any references, and I could tell that most of the blog authors had used secondary sources (other blogs or summary articles) instead of looking at the research evidence themselves. This can be fine, but sometimes it’s a bit like playing telephone: You just keep repeating the same facts over and over without checking to see if the evidence has changed or if the summary you are parroting was accurate in the first place. I’d like to think that my blog article is a very accurate assessment of the research evidence on GBS in pregnancy—translated into regular language so that women and their family members can understand the evidence. 

SM: What are you going to write about next?

RD: I don’t know!! What would YOU like to see me write about?

SM: I want to thank you Rebecca, for your contributions to Science & Sensibility and for sharing Evidence Based Birth with the world!  I know that these articles take a huge amount of time and you are very diligent and conscientious about researching the literature and providing only the best analysis possible,  and seeking out experts on the topic to help you really be sure that you are offering the best of the best of information.  I always enjoy reading your blog and find it a great source of information for my doula and CBE students and my birth doula clients as well. I know that I speak for all the readers here on Science & Sensibility when I say, keep on keeping on!  Do please let Rebecca know what you would like her to write about next!   

Sharon Muza ACOG, American Academy of Pediatrics, Babies, Childbirth Education, Evidence Based Medicine, Guest Posts, informed Consent, Maternity Care, Medical Interventions, New Research, Newborns, NICU, Push for Your Baby, Research antibiotics, Evidence Based Birth, GBS, group B strep, guest post, informed Consent, newborns, prenatal testing, Rebecca Dekker, research, Sharon Muza, tests in pregnancy

Today, Rebecca Dekker, PhD, RN, APRN of Evidence Based Birth shares a quick but very effective video tutorial on how to use the Cochrane Library to find evidence based information on maternity care topics.  Free and full access to the Cochrane Library is a Lamaze International member benefit and I value the information I am able to find there.  For more information on the Cochrane Collaboration, please see my recent post  celebrating the 20th anniversary of the Cochrane and sharing a bit about the history behind it. 

What other topics would you like covered in a video tutorial?  Rebecca is looking for more suggestions for the next video tutorial!  Also,  let us know how you use the Cochrane Library and please share other favorite sources you also use to find evidence based information on birth topics you are researching.

Sharon Muza Childbirth Education, Evidence Based Medicine, Maternity Care, Research Cochrane Collaboration, Evidence Based Medicine, Lamaze International, Rebecca Dekker, video tutorial

By Rebecca Dekker, PhD, RN, APRN of Evidence Based Birth

Do you talk about perineal massage with your students, clients and patients and state that perineal massage during pregnancy will/will not reduce tearing during birth?  today, Rebecca Dekker, of Evidence Based Birth takes a look at the research on perineal massage during pregnancy and provides information on the outcomes for women who practiced this and those who didn’t.  Does the research support what you have been saying? – Sharon Muza, Community Manager

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Tearing during childbirth is a common occurrence among women who have a vaginal birth. In studies where the use of episiotomies was restricted, the rate of spontaneous tearing was recorded to be anywhere from 44-79% (Soong and Barnes 2005; Dahlen, Homer et al. 2007). Studies have consistently shown that women are more likely to experience tearing during a first vaginal birth and with forceps and vacuum assistance (Aasheim, Nilsen et al. 2011).

Spontaneous tears can be classified as first, second, third, or fourth degree tears. First degree tears involve only the perineal skin, while second degree tears involve both the skin and the perineal muscle. Third degree tears involve the anal sphincter, while fourth degree tears involve the anal sphincter and tissues. Third and fourth degree tears happen at 0.25% to 2.5% of spontaneous vaginal births (Byrd, Hobbiss et al. 2005; Groutz, Hasson et al. 2011).

Women are more likely to have a third or fourth degree tear if they are giving birth vaginally for the first time, if a baby is in the posterior position or has a heavier birth weight, and if forceps, vacuum, or episiotomy are used (Christianson, Bovbjerg et al. 2003; Groutz, Hasson et al. 2011; Hirayama, Koyanagi et al. 2012).

What is perineal massage?

It is thought that massaging the perineum during pregnancy can increase muscle and tissue elasticity and make it easier for a mother to avoid tearing during a vaginal birth. Typically, women are taught to spend about 10 minutes per day doing perineal massage, starting at about 34-35 weeks of pregnancy. Women are taught to insert 1-2 lubricated fingers about 2 inches into the vagina and apply pressure, first downward for 2 minutes, and then sideways for 2 minutes. The massage can be done by the woman or her partner, and sweet almond oil is sometimes used for lubrication (Labrecque, Eason et al. 1999).

What is the evidence for perineal massage?

In 2006, Beckmann and Garrett combined the results from four randomized, controlled trials that enrolled 2,497 pregnant women. Three of these studies involved only women without a previous vaginal birth (mostly first-time moms). One study enrolled women with and without a previous vaginal birth. All four of the studies were of very good quality.

Beckmann and Garrett found that women who were randomly assigned to do perineal massage had a 10% decrease in the risk of tears that required stitches (aka “perineal trauma”), and a 16% decrease in the risk of episiotomy—but these findings were only true for first-time moms.

It is important for you to understand that this is a 10% reduction in relative risk, and relative risk is different than absolute risk. Let me give you an example. Say you are a first-time mom, and let’s pretend your absolute risk of perineal trauma is 50%. A 10% decrease in relative risk means that your absolute risk decreases by 5% (because .5 X .1 = .05). So for you, doing perineal massage reduces your absolute risk of perineal trauma from 50% to 45%.

*As a side note, all of the numbers I am reporting below are changes in relative risk.

Importantly, for second-time moms who had already had a vaginal birth, prenatal perineal massage did not reduce the risk of perineal trauma (any tearing requiring stitches). However, second-time moms who massaged did report a 32% decrease in the risk of ongoing perineal pain at 3 months post-partum.

Surprisingly, Beckmann and Garrett found that the more frequently women used perineal massage, the less likely they were to see any benefits. Women who massaged an average of 1.5 times per week had a 17% reduced risk of perineal trauma and a 17% reduced risk of episiotomy. Women who massaged between 1.5-3.4 times per week had an 8% reduced risk of perineal trauma.

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Interestingly, women who massaged > 3.5 times per week experienced NO benefits and had a longer pushing phase of labor by an average of 10 minutes. So basically the finding was: the less frequent the massage, the better off the outcomes. However, this finding was unexpected, and the researchers had a hard time explaining it. I think we should interpret this result with caution, because in the largest clinical trial on perineal massage (included in Beckmann and Garrett’s review), Labrecque et al. (1999) found that the more often women did the massage, the more likely they were to avoid any tears.

Other results: 

There were no differences between women who did prenatal perineal massage and those who did not with regard to:

• • First degree tears
• • Second degree tears
• • Third or fourth degree trauma
• • Use of forceps or vacuum during delivery
• • Sexual satisfaction 3 months post-partum
• • Pain with sexual intercourse 3 months post-partum
• • Uncontrolled loss of urine or bowel movements 3 months postpartum

Wait, I’m confused. You say that there was a significant decrease in perineal trauma requiring suturing. But there was no difference in 1^st, 2^nd, 3^rd, or 4^th degree tears. How can this be?

It’s important for you to understand that perineal trauma is an “umbrella” category that means all types of trauma requiring stitches, including episiotomies. Perineal massage during pregnancy decreased the overall risk of perineal trauma (the umbrella outcome), but the effect was too weak to see any difference with each of the individual outcomes (first degree, second degree, etc.). Also, the researchers think that the overall decrease in perineal trauma may have been due to the decreased episiotomy rate in the perineal massage group.

Why would perineal massage during pregnancy reduce the rate of episiotomies, but not tears?

The researchers guess that the women who were trained in perineal massage were highly motivated to birth with an intact perineum, so maybe they were more likely to refuse an episiotomy. Fewer episiotomies would then mean fewer incidents of trauma requiring stitches.

So what can we learn from the evidence?

During pregnancy, massage of the perineum can reduce the risk of tearing requiring stitches, but this benefit is only seen in moms giving birth vaginally for the first time. It is thought that most of the decreased risk of perineal trauma was due to a decrease in the episiotomy rate. In the largest study included in this review (Labrecque et al., 1999), there was an overall episiotomy rate of 38%. In the U.S., 25% of women have an episiotomy during a vaginal birth (Declercq, Sakala et al. 2007), and rates are even lower for some providers.  It is possible that these research findings might not apply to birth settings where episiotomies are extremely rare.

Second time moms who use perineal massage will not see any decrease in their risk of tearing, but they may reduce their risk of ongoing perineal pain at 3 months postpartum.

So in summary, for first-time moms only:

Perineal massage during pregnancy

↓

Decreased risk of episiotomy

↓

Decreased risk of trauma requiring stitches

If women choose to use perineal massage during pregnancy, there is no consensus on the amount of massage needed to reduce the risk of tearing.

Questions for discussion: Do you recommend prenatal perineal massage to others? Have your thoughts about this intervention changed after reading this article? 

References

Aasheim, V., A. B. Nilsen, et al. (2011). “Perineal techniques during the second stage of labour for reducing perineal trauma.” Cochrane Database Syst Rev(12): CD006672.

Beckmann, M. M. and A. J. Garrett (2006). “Antenatal perineal massage for reducing perineal trauma.” Cochrane Database Syst Rev(1): CD005123.

Byrd, L. M., J. Hobbiss, et al. (2005). “Is it possible to predict or prevent third degree tears?” Colorectal Dis 7(4): 311-318.

Christianson, L. M., V. E. Bovbjerg, et al. (2003). “Risk factors for perineal injury during delivery.” Am J Obstet Gynecol 189(1): 255-260.

Dahlen, H. G., C. S. Homer, et al. (2007). “Perineal outcomes and maternal comfort related to the application of perineal warm packs in the second stage of labor: a randomized controlled trial.” Birth 34(4): 282-290.

Declercq, E. R., C. Sakala, et al. (2007). “Listening to Mothers II: Report of the Second National U.S. Survey of Women’s Childbearing Experiences: Conducted January-February 2006 for Childbirth Connection by Harris Interactive(R) in partnership with Lamaze International.” J Perinat Educ 16(4): 9-14.

Groutz, A., J. Hasson, et al. (2011). “Third- and fourth-degree perineal tears: prevalence and risk factors in the third millennium.” Am J Obstet Gynecol 204(4): 347 e341-344.

Hirayama, F., A. Koyanagi, et al. (2012). “Prevalence and risk factors for third- and fourth-degree perineal lacerations during vaginal delivery: a multi-country study.” BJOG 119(3): 340-347.

Labrecque, M., E. Eason, et al. (1999). “Randomized controlled trial of prevention of perineal trauma by perineal massage during pregnancy.” Am J Obstet Gynecol 180(3 Pt 1): 593-600.

Soong, B. and M. Barnes (2005). “Maternal position at midwife-attended birth and perineal trauma: is there an association?” Birth 32(3): 164-169.

About Rebecca Dekker

Rebecca Dekker, PhD, RN, APRN, is an Assistant Professor of Nursing at a research-intensive university and author of www.evidencebasedbirth.com. Rebecca’s vision is to promote evidence-based birth practices among consumers and clinicians worldwide. She publishes summaries of birth evidence using a Question and Answer style.

Sharon Muza Childbirth Education, Evidence Based Medicine, Guest Posts, Research Childbirth Education, episiotomy, Evidence Based Birth, guest posts, how to avoid an episiotomy, Perineal Massage, Perineum, Rebecca Dekker, research

Today’s post is a fascinating interview that took place between Rebecca Dekker, PhD, RN, APRN of Evidence Based Birth and Kyoung Suk Lee, PhD, MPH, RN, APRN. Rebecca asked Dr. Lee to provide a reiew of the Wax Home Birth Meta-Analysis, as an “unbiased outsider”, but highly skilled researcher.  Dr. Lee’s comments and critique are fascinating and provided me with many further thoughts.  Please enjoy Rebecca’s interview and share your comments. – SM

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http://www.flickr.com/photos/eyeliam/7353095052/

Shortly after starting my website, www.evidencebasedbirth.com, I had several people ask me if I could write an article about the research evidence on home birth. However, I was hesitant to do so for several reasons. Mainly, I was worried that I could not look at the evidence in an objective manner. My husband and I had recently chosen a home birth for our second child. I was worried that it would be difficult to objectively examine the research evidence on home birth, given my personal experience. The blogosphere is full of people who are strongly pro-home birth or anti-home birth, and their evaluations of the evidence are usually written through the lens of their own biases. I didn’t want to add to the plethora of biased articles already out there.

Then I had a sudden burst of inspiration. What if I asked one of my colleagues—who has no biases about childbirth—to review the home birth literature for me? In particular, I wanted to find someone who could review the Wax home birth meta-analysis (Wax, Lucas et al. 2010) and give me a fair assessment of its scientific value.

I chose the Wax meta-analysis for this review because in 2011, the American Congress of Obstetricians and Gynecologists emphasized the results of the Wax study in its official statement on home birth. Their statement said: “Women inquiring about planned home birth should be informed of its risks and benefits based on recent evidence. Specifically, they should be informed that although the absolute risk may be low, planned home birth is associated with a twofold to threefold increased risk of neonatal death when compared with planned hospital birth.”(ACOG, 2011)

Dr. Kyoung Suk Lee, PhD, MPH, RN, APRN

It did not take me long to figure out who I would ask to review the Wax study. Dr. Kyoung Suk Lee is considered by her colleagues to be a rising star in the field of cardiovascular research. She recently graduated with a PhD in Nursing, and she just accepted a job at a research university. People who work with Dr. Lee say that she is extremely intelligent, hard-working, and a future leader in her field. Dr. Lee’s expertise has been recognized with research awards from the Heart Failure Society of America, the Society for Heart-Brain Medicine, and the Cleveland Clinic Heart-Brain Institute, among others. She has published her work in nursing and cardiology journals. Furthermore, I knew that Dr. Lee did not have any biases about childbirth, home birth, or hospital birth. I asked Dr. Lee if she would be willing to review the Wax meta-analysis for me, and she kindly agreed.

What follows is my interview of her about the study and its results (RD in bold, KSL unbolded).

Do you have any biases or conflicts of interest related to home or hospital birth?

I do not have any biases related to home or hospital birth.

Could you summarize the methods and results of the Wax study?

The purpose of this meta-analysis was to compare maternal and neonatal outcomes between planned home-and hospital-births.

Using an electronic database search and bibliography search, the authors retrieved 237 articles and included 12 articles in their meta-analyses. Of 12 articles included, 3 were conducted after 2000 while 9 were conducted before 2000. Of 12 articles, 2 were conducted in the US (one was a retrospective design) while 10 were conducted outside US.

Women in the planned home birth group had better maternal outcomes than women in the planned hospital group. They had fewer interventions such as epidurals and episiotomies, and lower morbidity (infection, 3^rd or 4^th degree lacerations, hemorrhages, and retained placenta). There were no differences in cord prolapse between the two groups.

For neonatal outcomes, babies born to women in the planned home birth group were less likely to experience prematurity and low birth weight. However, babies born to women in the planned home birth group were more likely to experience neonatal death compared to women in hospital birth.

What is the difference between neonatal and perinatal mortality? What does this have to do with the results?

Based on the definitions given by the authors, neonatal mortality was defined as “death of live born child within 28 days of birth.” This is a subset of an overall outcome– perinatal mortality, which was defined as “stillbirth (of at least 20 weeks or 500g) or death of live born child within 28 days of birth.”

According to the authors, there were no differences in perinatal death (the overall outcome) between planned home birth and hospital birth groups. However, homebirth was associated with 2 times higher risk for neonatal death (the subset of deaths occurring 28 days after birth) in all infants and 3 times higher risk for neonatal death in infants who did not have any congenital birth defects.

Interestingly, if you look at page 243.e3, the authors did a sensitivity analysis. In this analysis, they excluded the studies that had home births that were not attended by certified midwives or certified nurse midwives. In this analysis, they found that there were no differences in neonatal deaths between the home birth and hospital birth groups. This means that in the studies in which midwives with certification of some kind attended home births, the outcomes were the same except there was no increase in the neonatal death rate. In my opinion, we have to pay attention to results of sensitivity analyses because this allows us to see the results based on studies which were definitely known to be eligible or clearly described their methods and outcomes.

What is your opinion on the scientific rigor of this meta-analysis?

One thing that was strange to me is the odds ratios (ORs) in the tables. For example, in table 2, under morbidity, the percentages of infection between home births and hospital births were 0.7 vs. 2.6 (its OR was 0.27) while percentages of perineal laceration were 42.7 vs. 37.1 (its OR was 0.66). To a researcher, these numbers don’t make sense.

Many of the studies included were older (half of the studies were conducted more than 20 years ago) so results may not reflect the current practice at home births or hospital births.

The authors did not provide detailed information on how they evaluated the quality of studies included, although they cited a paper describing the method of study evaluation. This makes it difficult if not impossible to determine whether the studies they included were of good or poor quality.

The authors mentioned that women with high risks would prefer hospital births so that it would expect that home births have better outcomes than hospital births in some maternal and neonatal outcomes. If this was a concern, I wonder why the authors didn’t just focus on only the studies that used matching methods, in order to minimize confounding factors.

What is the difference between relative risk and absolute risk, and how does that apply to women who want to have a home birth?

Absolute risk is the probability of something occurring. They may be expressed as percentages or ratios. For example, neonatal mortality rate in the United States is 2.01 per 1,000 live births. This is .201 percent (2.01/1000 = .201/100).

http://www.flickr.com/photos/mikeporcenaluk/3789756395/

Relative risk is a comparison between different risk levels, such as the neonatal mortality rate of home birth compared to the neonatal mortality rate of hospital birth. The researchers found that there was a higher relative risk in neonatal mortality at home births compared to hospital births, but the overall absolute risk for both was small.

How can women know whether the Wax study results would be applicable to their own individual situation?

Meta analysis is one way to generalize findings from different studies. However, women and clinicians should interpret these results cautiously because the studies included were very different from one another and some of the studies included may not have been of good quality. Also, it would be important to note that the overall neonatal death rate that they report reflects home births that were attended by midwives as well as those that may not have had any kind of certified midwife present.

Because this study seems to have some flaws, the conclusion is tentative. I do not know if this article has any implications for pregnant women.

What do you think is the value of asking someone with no conflicts of interest to evaluate controversial research? Does Dr. Lee’s even-handed critique make you view the results of this study any differently? How do you feel about Dr Lee’s conclusion that the study’s results are tentative, and that the Wax study might not have any implications for pregnant women? Please share your thoughts and comments with other readers.

References

(2011). “ACOG Committee Opinion No. 476: Planned home birth.” Obstetrics and gynecology 117(2 Pt 1): 425-428.

Wax, J. R., F. L. Lucas, et al. (2010). “Maternal and newborn outcomes in planned home birth vs planned hospital births: a metaanalysis.” Am J Obstet Gynecol 203(3): 243 e241-248.

About Rebecca Dekker

Rebecca Dekker, PhD, RN, APRN, is an Assistant Professor of Nursing at a research-intensive university and author of www.evidencebasedbirth.com. Rebecca’s vision is to promote evidence-based birth practices among consumers and clinicians worldwide. She publishes summaries of birth evidence using a Question and Answer style.

Sharon Muza Babies, Childbirth Education, Evidence Based Medicine, Guest Posts, Home Birth, Metaanalyses, Midwifery, New Research, NICU, Research ACOG, ACOG and homebirth, ACOG Committee position papers, guest post, Home Birth, home birth vs. hospital birth, interviews, is home birth safe?, Kyoung Suk Lee, meta-analysis, Rebecca Dekker, research, Wax study

By Rebecca L. Dekker, PhD, RN, APRN

Today’s post on the Evidence for Induction for Low Amniotic Fluid in a Healthy Pregnancy is a guest post by blogger Rebecca Dekker, owner of  the fairly new blog in the birth world, Evidence Based Birth that has been  very well received and enjoyed by many.  Look for an interview with Rebecca in an upcoming post where we will learn how this Assistant Professor of Nursing who teaches pathopharmacology and studies depression in patients with heart failure ended up writing the Evidence Based Birth blog appreciated by birth professionals.  I look forward to future posts and collaboration with Rebecca and thank her for her contribution today.- SM

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This question came from one of my readers:

“Low fluid seems to be the new “big baby” for pushing for induction. What does the research say about low fluid at or near term? From what I’ve been able to see in research summaries at least, there appears to be no improved outcome for babies, but I’d love to see the research really hashed out. I’m also curious about causes of low fluid (theorized or known), risks of low fluid, and perhaps as important if not more so, measurements of low fluid.”

This is a great question and I felt like it was a perfect topic for my first article for Science and Sensibility. Standard of practice in the U.S. is to induce labor at term if a mother has low amniotic fluid in an otherwise healthy pregnancy. In fact, 95% of physicians who practice maternal-fetal medicine feel that isolated oligohydramnios—low amniotic fluid in an otherwise healthy pregnancy—is an indication for labor induction at 40 weeks (Schwartz, Sweeting et al. 2009).

But what is the evidence for this standard birth practice? Let’s take a look at the evidence together.

First of all, what is oligohydramnios?

Oligohydramnios means low fluid inside the amniotic sac.

(oligo = little, hydr = water, amnios = membrane around the fetus, or amniotic sac).

Not sure how to pronounce oligohydramnios? Click here.

It is standard of care in the U.S. to induce women with isolated oligohydramnios at term.
Image Source drewesque 

What is amniotic fluid, and what does it do?

During pregnancy, the baby is surrounded by a liquid called amniotic fluid. Amniotic fluid helps protect the baby from trauma to the mother’s abdomen. Amniotic fluid cushions the umbilical cord, protects the baby from infection, and provides fluid, space, nutrients, and hormones to help the baby grow (Brace 1997).

During the second half of pregnancy, amniotic fluid is made up of the baby’s urine and lung secretions. This liquid originally came from the mother, and then flowed through the placenta, to the baby, and out through the baby’s bladder and lungs (Brace 1997).

This same amniotic fluid is then swallowed by the baby and re-absorbed by the lining of the placenta. Because the mother’s fluid levels are the original source of amniotic fluid, changes in the mother’s fluid status can result in changes in the amount of amniotic fluid. Amniotic fluid levels increase until the mother reaches about 34-36 weeks, and then levels gradually decline until birth (Brace 1997).

What can cause low amniotic fluid at term?

Both mother and baby factors can contribute to low amniotic fluid at term.

Mother factors:

• If the mother is dehydrated, this may lower the amniotic fluid levels. (Patrelli, Gizzo et al. 2012)
• Women are more likely to be diagnosed with low amniotic fluid levels during the summer, possibly because of dehydration. (Feldman, Friger et al. 2009)
• If a woman with low amniotic fluid levels at term drinks at least 2.5 Liters of fluid per day, she increases the likelihood that her amniotic fluid levels will be back up to normal by the time of delivery. (Patrelli, Gizzo et al. 2012)
• If the mother rests on her left side before or during the fluid measurement, this can increase amniotic fluid levels. (Ulker, Temur et al. 2012)
• If the mother’s water has broken (membranes ruptured), this will lead to a decrease in amniotic fluid. (Brace 1997)
• If the mother’s placenta is not acting sufficiently anymore, this may lead to a decrease in amniotic fluid. When this happens, it may be because the mother has a serious condition such as pre-eclampsia or intrauterine growth restriction. (Beloosesky and Ross 2012)

Baby factors:

• If the baby has a problem with the urinary tract or kidneys, this may decrease the flow of urine. (Brace 1997)
• In the 14 days before the start of spontaneous labor, the baby’s urine output starts to decrease. (Stigter, Mulder et al. 2011)
• As the baby gets closer to term, the baby swallows more amniotic fluid, thus leading to a decline in fluid levels. (Brace 1997)
• If the baby is post-term (after 42 weeks), he or she begins to swallow significantly more fluid, contributing to a decline in amniotic fluid. (Brace 1997)
• If the baby has a birth defect, he or she may swallow significantly more fluid, leading to low amniotic fluid levels. (Beloosesky and Ross 2012)

What is the best way to measure amniotic fluid levels?

The gold-standard method is to inject the amniotic sac with dye and then take samples of the amniotic fluid to check the dilution. However, this method is very invasive. So the most commonly used methods instead are 2 ultrasound techniques:  the amniotic fluid index (AFI) and the single deepest pocket (Gilbert 2012).

To calculate the AFI, the technician divides the uterus into 4 areas. The largest fluid pocket in each area is measured, and then these 4 numbers are added make up the AFI. An AFI value of 5 cm or less is considered oligohydramnios. With the single deepest pocket method, the technician looks for the largest pocket of amniotic fluid in the uterus. If the largest pocket is less than 2 cm by 1 cm, then that is considered a diagnosis of oligohydramnios (Nabhan and Abdelmoula 2009).

It is important to understand that amniotic fluid levels exist on a continuum and that there is no agreement among researchers about the cut-off value that predicts poor outcomes—the AFI level of 5 was arbitrarily chosen to define oligohydramnios (Nabhan and Abdelmoula 2009). Furthermore, a large body of research has shown that both AFI and single deepest pocket are poor predictors of true amniotic fluid volume. For example, the AFI catches only 10% of all cases of true oligohydramnios (10% sensitivity)(Gilbert 2012).

There are several factors that make it difficult to get an accurate ultrasound measurement. As fluid levels decrease, ultrasound results become less accurate. Inexperience on the part of the technician can reduce the accuracy of the test results, as well as the amount of pressure that the technician puts on the ultrasound probe. The position of the baby can also affect the accuracy of the results. (Nabhan and Abdelmoula 2009; Gilbert 2012).

So which is the best way to measure amniotic fluid?

In a Cochrane review, researchers combined the results from 5 randomized controlled trials with more than 3,200 women. In these studies, women were randomized to either the AFI method or the single deepest pocket method. Researchers found that when the AFI is used to measure amniotic fluid, women were 2.4 times more likely to be diagnosed with oligohydramnios, 1.9 times more likely to be induced, and 1.5 times more likely to have a Cesarean for fetal distress without any corresponding improvement in infant outcomes. The researchers concluded that the single deepest pocket measurement has fewer risks and should be the preferred way to measure amniotic fluid (Nabhan and Abdelmoula 2009).

What is the clinical significance of low amniotic fluid when a mother reaches 37 or more weeks?

In 2009, 91% of physicians believed that isolated oligohydramnios, or low amniotic fluid in an otherwise healthy pregnancy at term, was a risk factor for poor outcomes (Schwartz, Sweeting et al. 2009).

In the U.S., 91% of maternal-fetal physicians believe that isolated oligohydramnios at term is a risk factor for poor outcomes, and 95% will recommend labor induction.
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However, this belief is not accurate. In early studies on amniotic fluid and outcomes, researchers included babies with congenital defects , women with pre-eclampsia or intrauterine growth restriction (IUGR), and women who were post-term (past 42 weeks) in their samples. These women and babies are more likely to have low amniotic fluid, and they are also much more likely to have poor outcomes. So although early researchers found that babies born to women with low amniotic fluid had higher perinatal mortality rates (Chamberlain, Manning et al. 1984), higher Cesarean rates for fetal distress, and lower Apgar scores (Chauhan, Sanderson et al. 1999), the poor outcomes were due to the complications—not the low amniotic fluid (Gilbert 2012).

So, if a woman has TRUE ISOLATED oligohydramnios at term, meaning low amniotic fluid in a healthy pregnancy with a healthy baby at term (between 37 and 42 weeks), what are the risks?

There is no evidence that isolated oligohydramnios at term is a risk factor for poor outcomes. However, induction for isolated oligohydramnios leads to higher Cesarean rates. In a systematic literature review, I found 5 studies from the last 10 years. I will discuss the 3 highest quality studies here. For results from all 5, you can see my findings summarized in this Google document table here.

1. Locatelli et al. (2003) studied 3,049 healthy pregnant women who were between 40 and 41.6 weeks pregnant. The purpose of this study was to find out if low amniotic fluid (defined as AFI ≤ 5) led to poor outcomes. Eleven percent of women had low amniotic fluid, and these women had higher induction rates (83% vs. 25%), higher Cesarean rates (15% vs. 11%), and higher Cesarean rates for non-reassuring fetal heart rates (8% vs. 4%). Babies born to women with low amniotic fluid were more likely to have birth weights beneath the 10^th percentile (13% vs. 6%). There were no differences between groups with meconium staining, meconium aspiration, umbilical artery pH <7, or Apgar scores. There was only one stillbirth (in the normal fluid group) for a true knot in the umbilical cord.

After controlling for the fact that some women were induced and some women were having their first baby, the researchers found no association between Cesarean for non-reassuring heart rate and amniotic fluid. This means that the inductions were probably responsible for the higher Cesarean rates in the low amniotic fluid group. However, when the researchers controlled for gestational age, they found that the association between low birth weight and low amniotic fluid remained significant. This means that women with low amniotic fluid were 2 times more likely to have a baby that is born beneath the 10^th percentile. These babies may have had undiagnosed fetal growth restriction (IUGR), which is a separate risk factor for poor outcomes.

1. Manzaneres et al. (2006) compared outcomes from 206 healthy pregnant women who were induced for isolated oligohydramnios at term and 206 healthy pregnant women with normal amniotic fluid levels who went into spontaneous labor.  The women in both groups delivered between 37 and 42 weeks. The researchers found that the low amniotic fluid group was more likely to require forceps or vacuum delivery (26% vs. 17%), Cesarean delivery (16% vs. 6%), and have non-reassuring fetal status during labor (8% vs. 2%). The non-reassuring fetal status may have been due to the induction medications, but this explanation was not proposed by the authors. There were no differences between groups with birth weight, Apgar scores, meconium staining, neonatal admissions, or umbilical cord pH. In summary, the authors found that inducing labor for isolated oligohydramnios at term increased Cesarean and operative vaginal delivery rates without any improvement in newborn outcomes.

1. There was one small pilot study done in which researchers randomized women with isolated oligohydramnios at term to induction or watchful waiting. The researchers randomly assigned 54 women who were 41 weeks pregnant to either induction or watchful waiting. There were no differences between groups in any outcomes, including birth weight, Cesarean delivery, Apgar scores, or neonatal admission. This study was limited by its small sample size and the fact that it only included women who were 41 weeks pregnant (Ek, Andersson et al. 2005).

So what is the evidence for induction because of low amniotic fluid (without any other complications) at term?

There is no evidence that inducing labor for isolated oligohydramnios at term has any beneficial impact on mother or infant outcomes. Based on the lack of evidence, any recommendation for induction for isolated oligohydramnios at term would be a weak recommendation based on clinical opinion alone.

In summary, this is what I found about low amniotic fluid in an uncomplicated pregnancy at term (37-42 weeks):

• Ultrasound measurement is a poor predictor of actual amniotic fluid volume
• The single deepest pocket method of measurement has fewer risks than the AFI
• Poor outcomes seen with low amniotic fluid are usually due to underlying complications such as pre-eclampsia, birth defects, or fetal growth restriction
• The main risk of low amniotic fluid at term in a healthy pregnancy is induction (and Cesarean delivery as a result of the induction) and potentially the risk of lower birth weight
• Current evidence does not support induction for isolated oligohydramnios at term

Are women in your local areas being induced for isolated oligohydramnios at term? Are consumers and clinicians aware of this evidence? What is the standard of practice for evaluating amniotic fluid in your local facilities, AFI or Single Deepest Pocket? How do you discuss this in your classes and with your patients, clients and students?

References

1. Beloosesky, R. and M. G. Ross. (2012). “Oligohydramnios.”   Retrieved 8/20/12, 2012, from www.UpToDate.com
2. Brace, R. A. (1997). “Physiology of amniotic fluid volume regulation.” Clin Obstet Gynecol 40(2): 280-289.
3. Chamberlain, P. F., F. A. Manning, et al. (1984). “Ultrasound evaluation of amniotic fluid volume. I. The relationship of marginal and decreased amniotic fluid volumes to perinatal outcome.” Am J Obstet Gynecol 150(3): 245-249.
4. Chauhan, S. P., M. Sanderson, et al. (1999). “Perinatal outcome and amniotic fluid index in the antepartum and intrapartum periods: A meta-analysis.” Am J Obstet Gynecol 181(6): 1473-1478.
5. Ek, S., A. Andersson, et al. (2005). “Oligohydramnios in uncomplicated pregnancies beyond 40 completed weeks. A prospective, randomised, pilot study on maternal and neonatal outcomes.” Fetal Diagn Ther 20(3): 182-185.
6. Feldman, I., M. Friger, et al. (2009). “Is oligohydramnios more common during the summer season?” Arch Gynecol Obstet 280(1): 3-6.
7. Gilbert, W. M. (2012). Amniotic Fluid Disorders. Obstetrics: Normal and Problem Pregnancies. S. G. Gabbe. Philadelphia, PA, Elsevier. 6.
8. Locatelli, A., P. Vergani, et al. (2004). “Perinatal outcome associated with oligohydramnios in uncomplicated term pregnancies.” Arch Gynecol Obstet 269(2): 130-133.
9. Nabhan, A. F. and Y. A. Abdelmoula (2009). “Amniotic fluid index versus single deepest vertical pocket: a meta-analysis of randomized controlled trials.” International journal of gynaecology and obstetrics: the official organ of the International Federation of Gynaecology and Obstetrics 104(3): 184-188.
10. Patrelli, T. S., S. Gizzo, et al. (2012). “Maternal hydration therapy improves the quantity of amniotic fluid and the pregnancy outcome in third-trimester isolated oligohydramnios: a controlled randomized institutional trial.” J Ultrasound Med 31(2): 239-244.
11. Schwartz, N., R. Sweeting, et al. (2009). “Practice patterns in the management of isolated oligohydramnios: a survey of perinatologists.” J Matern Fetal Neonatal Med 22(4): 357-361.
12. Stigter, R. H., E. J. Mulder, et al. (2011). “Fetal urine production in late pregnancy.” ISRN Obstet Gynecol 2011: 345431.
13. Ulker, K., I. Temur, et al. (2012). “Effects of maternal left lateral position and rest on amniotic fluid index: a prospective clinical study.” J Reprod Med 57(5-6): 270-276.

Rebecca Dekker, PhD, RN, APRN, is an Assistant Professor of Nursing at a research-intensive university and author of www.evidencebasedbirth.com. Rebecca’s vision is to promote evidence-based birth practices among consumers and clinicians worldwide. She publishes summaries of birth evidence using a Question and Answer style. You can contact Rebecca via email here.

Sharon Muza Evidence Based Medicine, Fetal Monitoring, Guest Posts, Healthy Birth Practices, Healthy Care Practices, informed Consent, Maternity Care, Medical Interventions, Systematic Review, Uncategorized AFI, Evidence Based Birth, Evidence Based Medicine, Fetal Monitoring, guest post, Healthy Birth Practices, induction, Oligohydramnios, prenatal ultrasound, Rebecca Dekker