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Flaws In Recent Home Birth Research May Mislead Parents, Providers

September 26th, 2013 by avatar

by Wendy Gordon, CPM, LM, MPH, MANA Division of Research, Assistant Professor, Bastyr University Dept of Midwifery

Midwife Wendy Gordon shares with Science & Sensibility readers why the recent home birth research using 5 minute Apgar scores does not produce reliable data that consumers can use to make a decision on where they would like to give birth.  Have you had a chance to read the study?  What were your conclusions? See if you agree with Wendy or had some different thoughts.  Share your opinion and thoughts with us in the comments section.  Thank you Wendy for providing information that can help us to assess the study and understand it better. Sharon Muza, Science & Sensibility Community Manager

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© http://www.mybirth.com.au/

A recent press release by the authors of a new study raised alarming headlines in a few media outlets, suggesting that babies born at home had a 10-fold higher death rate than babies born in the hospital. I’ve written previously about reliability concerns with the use of birth certificates in this study. In this post, we’ll go more in-depth with some of its other flaws. Let’s start with the fact that the authors did not examine stillbirths.

Apgar scores and stillbirth

The new study by Grunebaum et al. (2013), in press with the American Journal of Obstetrics & Gynecology, examined birth certificate data for almost 14 million births between 2007 and 2010 looking for differences in outcomes between home and hospital births. They did not look at “stillbirths,” perinatal, intrapartum or neonatal deaths. They looked at 5-minute Apgar scores of zero, and led the readers of their press release to believe that this meant that the babies died during or shortly after labor, due entirely to their choice of birthing at home.

When we examine a little more closely what it means to have a 5-minute Apgar score of zero, we might find that it does include some babies who died shortly after birth. We might also find a number of babies who had lethal congenital anomalies, who would not have survived no matter where they were born or who attended the birth; there may be important differences between home and hospital populations with regard to whether these anomalies were detected prenatally and whether parents changed their birth plans because of it. There may also be some babies who were successfully resuscitated after the 5-minute Apgar score was assessed. While the authors conceded in the study that their analysis could have included these births, as well as babies who died before labor even began, the terminology used in their press release is highly misleading.

A rigorous study that actually examined deaths would have excluded births with outcomes that had nothing to do with place of birth or attendant. Several well-designed studies have done just that and have found no differences in mortality rates between planned home and hospital births, and often fewer low 5-minute Apgar scores among planned home births attended by midwives (Ackermann-Liebrich et al., 1996; Olsen, 1997; Janssen et al., 2002; Hutton et al., 2009; Janssen et al., 2009). Grunebaum does not mention that their findings are actually the opposite of what several rigorous studies have already determined.

Absolute vs relative risk

I’ve also written previously about the dangers of reporting relative risks (“ten times higher!”) without acknowledging that the absolute risk of the complication is actually very, very low. Even if Grunebaum’s study had appropriately excluded outcomes that had nothing to do with place of birth, and even if their source of data was reliably accurate — no one is served by omitting the fact that 5-minute Apgar scores of zero are exceedingly rare.

Some of the raw numbers that Grunebaum reports in the study are so low — less than a dozen events within tens of thousands of births, in some cases — that it is hard to imagine how practitioners could use this information to draw any meaningful conclusions whatsoever about clinical practice.

Even with all of the flaws in this study, the rate of zero Apgars in the “home midwife” category in this study was 1.6/1000. This is a very low number. If these results were valid, it would be these absolute risks that mothers and families should be informed about, and honest discussions should be had regarding why there might be a higher risk in the home setting so that families can make the best decisions for themselves about all of the risks and benefits that come with location of birth.

Transfers not accounted for in “planned” home births

A concern that is often raised by anti-homebirth activists is that births that start out as planned home births but transfer to the hospital in labor are actually counted as hospital statistics in birth certificate data. To be fair, these births likely do have worse outcomes. Although most transfers are for non-urgent reasons such as stalled labor or desire for pain relief (Johnson & Daviss, 2005), some transfers occur because medical assistance is needed and the appropriate place to be is in the hospital.

But let’s look at the real impact of these transports. U.S. data shows that about 10% of planned home births result in transport to the hospital during labor (Johnson & Daviss, 2005). Even if Grunebaum was able to accurately capture planned home births and that number truly was 67,429, we could reasonably assume that about 10% of those babies (6743) were born in the hospital. Those babies account for less than 0.05% of the 14 million babies born in the hospital. Even if every single one of those babies had a 5-minute Apgar score of zero, Grunebaum’s rate of zero Apgars in the hospital would increase from 0.25/1000 to 0.49/1000. In reality, only a very small proportion of home birth transports actually do result in such an adverse outcome, and thus essentially have a negligible effect on hospital outcomes.

On the other hand, even a small percentage of misclassified outcomes in the home birth category have a dramatic impact. Because the number of home births in the U.S. is small, the inclusion of prenatal stillbirths, congenital anomalies and unplanned, unattended home births in the “home midwife” category is likely to have an appreciable effect on the negative outcomes examined here. Furthermore, the 10% of home birthers who transport to the hospital and have positive outcomes there are not appropriately attributed to the planned home birth group either. The truth about the safety of home birth simply cannot be determined in this way.

Reliability of birth certificates

I wrote my initial reaction to Grunebaum et al’s study last week when their press release came out. I expressed concerns about the low reliability and validity of birth certificates for drawing conclusions about rare outcomes. Grunebaum’s own data shows that over 10% of “home midwife” deliveries had no information on the birth certificate about the mother’s parity and had to be excluded from their calculations, while only 0.2-0.5% of hospital or birth center deliveries were missing parity data; this strongly suggests that something is amiss with the “home midwife” data.

Epidemiologists and birth certificate scholars have made their concerns about reliability and validity exceedingly clear in an enormous body of literature over the last few decades, and in fact, expressed these concerns directly to Frank Chervenak (co-author on this study) earlier this year when he presented this very data at the Institute of Medicine’s workshop on Research Issues in the Assessment of Birth Settings (IOM & NRC, 2013, p.143). The fact that these authors were clearly warned about the low quality of their data regarding both low Apgar scores — and especially seizures — but chose to push ahead with publication without addressing them, suggests other motivations.

Summary

Families deserve to have the best possible information with which to make decisions about where to have their babies. Grunebaum and co-authors miss the mark by a wide margin with the methodology and conclusions of this study.

To learn more about existing, well-designed home birth studies, read here. To learn more about the MANA Stats Project, which provides researchers with a dataset of more than 24,000 planned home birth and birth center births, read here. And watch for new research based on the MANA Stats dataset 2004-2009. Two articles are in press and two more are under review in peer-reviewed journals.

References:

Ackermann-Liebrich, U., Voegeli, T., Gunter-Witt, K., Kunz, I., Zullig, M., Schindler, C., Maurer, M. & Zurich Study Team. (1996). Home versus hospital deliveries: follow up study of matched pairs for procedures and outcome. BMJ 313:1313-1318.

Declercq, E., MacDorman, M. F., Menacker, F., & Stotland, N. (2010). Characteristics of planned and unplanned home births in 19 states. Obstetrics & Gynecology 116(1):93-99.

Grunebaum, A., McCullough, L. B., Sapra, K. J., Brent, R. L., Levene, M. I., Arabin, B., & Chervenak, F. A. (2013). Apgar score of 0 at 5 minutes and neonatal seizures or serious neurologic dysfunction in relation to birth setting. Am J Obstet Gynecol, 209:x-ex x-ex.

Hutton, E. K., Reitsma, A. H., & Kaufman, K. (2009). Outcomes associated with planned home and planned hospital births in low-risk women attended by midwives in Ontario, Canada, 2003-2006: a retrospective cohort study. BIRTH 36(3):180-189.

IOM (Institute of Medicine) and NRC (National Research Council). (2013). An Update on Research Issues in the Assessment of Birth Settings: Workshop Summary. Washington, DC: The National Academies Press.

Janssen, P. A., Lee, S. K., Ryan, E. M., Etches, D. J., Farquharson, D. F., Peacock, D., & Klein, M. C. (2002). Outcomes of planned home births versus planned hospital births after regulation of midwifery in British Columbia. CMAJ 166(3):315-323.

Janssen, P. A., Saxell, L., Page, L. A., Klein, M. C., Liston, R. M., & Lee, S. K. (2009). Outcomes of planned home birth with registered midwife versus planned hospital birth with midwife or physician. CMAJ 181(6-7):377-383.

Johnson, K. C. & Daviss, B. A. (2005). Outcomes of planned home births with certified professional midwives: large prospective study in North America. BMJ 330:1416-

Olsen, O. (1997). Meta-analysis of the safety of home birth. BIRTH 24(1):4-13.

About Wendy Gordon

Wendy Gordon, LM, CPM, MPH is a midwife, mother and educator in the Seattle area.  She helped to build a busy, blended homebirth practice of nurse-midwives and direct-entry midwives in Portland, Oregon for eight years before recently transitioning to Seattle.  She is a Coordinating Council member of the Midwives Alliance Division of Research, a board member of the Association of Midwifery Educators, and teaches at the Bastyr University Department of Midwifery.

ACOG, Childbirth Education, Guest Posts, Home Birth, Midwifery, Newborns, Research , , , , , , ,

Jumping to conclusions: Popular media spins an abstract into headlines.

February 23rd, 2012 by avatar

A new study has been making the rounds of the popular news sites.  The abstract – 65: Neonatal outcomes associated with intended place of birth: birth centers and home birth compared to hospitals  The abstract of the study is published in AJOG It was presented at the Society for Maternal-Fetal Medicine 32nd Annual Meeting.

It is strange that this abstract is getting so much attention. With only an abstract available it is impossible to judge the study’s merits. We look forward to the publication of the study. At this point we have to reserve judgment for later.  We simply don’t have the data available to determine the strength or validity of the study.  That said, it is amazing that the findings presented in the abstract are getting so much attention.

Here are some of the many articles, with varying perspectives, discussing it: 

I found this article to be neutral verging on steering families toward hospital birth:

 “Babies born at home were more than twice as likely to have an Apgar score of under 7 as children born in a hospital or at a birthing center, and also had double the chances of having a seizure….

The overall number of kids who had seizures was low — less than 1 percent at any location.

Prior research has shown that babies with lower Apgar scores are more likely to have complications after birth, such as needing breathing assistance, going to the ICU, having seizures or having developmental issues, Cheng said.”

Study Weighs Pros, Cons of Home or Hospital Birth: More seizures, lower Apgar scores found in home or hospital birth  

 

This article has a positive spin for homebirth:

 “But when a certified midwife was present, it seems babies born at home may fare as well as those born in hospitals, said study researcher Dr. Yvonne Cheng, an obstetrician and gynecologist at the University of California, San Francisco.

“It’s not just about where you deliver, but perhaps who you deliver with,” Cheng said.

Home births are known to be associated with fewer obstetric interventions — that is, women in labor at home receive fewer epidurals and less pain medication.

Women must weigh the benefits of home births against the risks to make an informed decision about where to give birth, Cheng said.”

Midwives make homebirth safer for babies  

 

 This article seems to treat the study in a neutral manner:

 “Women who have home births or plan to deliver at home have lower rates of cesarean delivery; however, their babies are more likely to have neonatal seizures and lower Apgar scores if a certified midwife is not in attendance, according to research presented here at the Society for Maternal-Fetal Medicine 32nd Annual Meeting.”

Home Births Associated With More Seizures, Lower Apgar Scores

 

This one uses bad data to back a claim:

“…recent evidence suggests that while the absolute risk of planned home births is low, such births carry a neonatal death rate at least twice as high as that of planned hospital births. Neonatal death occurred less than once in 1,000 hospital births, compared with two in 1,000 home births, said an American Journal of Obstetrics & Gynecology meta-analysis published in September 2010.”

Home births rise despite higher neonatal mortality rate: Although the vast majority of deliveries occur in hospitals, more women who want a less institutional experience are opting to give birth at home.

This AMA article is citing the Wax et al study.  Science and Sensibility has discussed the vast array of errors and misinformation in the Wax study on four separate occasions:

Others have cited Wax et al, although not explicitly such as this one: Homebirths up Dramatically, but are they safe?

There were numerous letters written to AJOG with regards to the flaws in the study, as well.  So, to have the Wax et al study brought up again is inappropriate and poor science.  It feels to me like a scare tactic or propaganda.

Given that we don’t have all the information, I question the journalistic integrity with which the articles above are written.  It’s always a good headline – about the dangers of home birth.  It’ll get links clicked, newspapers sold and running commentary on social media sites.  However, without proper analysis of the data things are potentially misrepresented.  Once we gain access to the full study, Science and Sensibility will be able to respond appropriately.

Some questions we hope to answer:

  • What data were used? How strong is the data set?
  • Many home births are not reported as such, so data will be lacking.  How is this accounted for?
  • Does the legal status of a homebirth midwife impact outcomes?  Especially because the author states that CNMs have better outcomes than do CPMs or DEMs. We are not aware of research that supports this.
  • Is it considered homebirth if the mother was transferred from home to hospital mid-labor if her intention was to have a home birth?

For more on recent perspectives on homebirth please visit the Homebirth Consensus Summit.

Let’s get the discussion going here.  What are your thoughts on homebirth?

Evidence Based Medicine, Guest Posts, Home Birth, Metaanalyses, Midwifery, News about Pregnancy, Research , , , , , , , , , , , , , , ,

The Weill Cornell Patient Safety Program: Too Good To Be True?

October 10th, 2011 by avatar

The Program in Question
In February of this year, amid much fanfare and publicity, the Department of Obstetrics and Gynecology at New York Presbyterian Hospital-Weill Cornell Medical Center published the results of their comprehensive obstetric patient safety program in the American Journal of Obstetrics and Gynecology. Titled, “Effect of a Comprehensive Obstetric Patient Safety Program on Compensation Payments and Sentinel Events” the article was immediately embraced by the media, politicians, legislators, obstetrician groups, and even many patient advocates as proof-positive that sentinel events and compensation payments could be drastically reduced through implementation of the Weill Cornell obstetric patient safety program (full citation: Grunebaum, A., Chervenak, F., Skupski, D.: Effect of a comprehensive obstetric patient safety program on compensation payments and sentinel events. Am J Obstet Gynecol 204. 97-105). A bill was quickly introduced to the State Senate mandating that the Weill Cornell program be replicated in every hospital across the state. With Governor Cuomo backing controversial legislation to cap non-economic jury damages, the article also became highly politicized, with both sides evidencing it for and against malpractice tort reform.

In the barrage of press releases and political commentary that followed the article’s release, much attention was given to, and yet little critical analysis was made of, the authors’ staggering claims. In the article, Drs. Grunebaum, Chervenak, and Skupski reported that, with implementation of a “comprehensive obstetric patient safety program” over a six-year period from 2003-2009:

 

  • Obstetric compensation payments dropped more than 99%, from an average of $27.69 million between 2003-2006 to $250,000 in 2009;
  • Sentinel events were eliminated entirely, with none reported in 2008 and 2009.

 

Sounds great, doesn’t it? Not so fast. Before we rush to insure the obstetricians, apply for a job, refer our expectant patients, or deliver babies ourselves at Weill Cornell, there are a few additional questions worth asking here. Shortly after the article was published, Kathleen Clark, a collaborative health care attorney and CEO of Servant Lawyership, Bob Latino, professional root cause analyst and CEO of Reliability Center, Inc., and I met to review the paper and offer feedback, not as clinicians, but as passionate advocates of patient safety and consumer engagement in the health care dialogue. Our analysis, “The Weill Cornell Patient Safety Program Study: Feedback from Patient Safety Advocates in Medicine, Law, and Root Cause Analysis,” was published this week in an AJOG letter-to-the-editor. The link to the full letter can be found here, however, with AJOG’s permission, I would like to share with you some of the questions we raised in response to Grunebaum, et al’s article:


What were the criteria used to classify an incident as a “sentinel event” in the study?
The Joint Commission defines “sentinel event” as “an unexpected occurrence involving death or serious physical or psychological injury, or the risk thereof,” however, the authors’ definition was much more narrowly defined: “at our institution, sentinel events included maternal deaths, and serious newborn injuries, including birth asphyxia and hypoxic, ischemic encephalopathy.” Such self-imposed restrictive criteria account for only the rarest and most extreme outcomes. Since sentinel events are the “tip of the iceberg,” a decrease in the number of sentinel events, small to begin with, may not indicate an appreciable improvement in the overall safety or quality of patient care.

 

How might a broader definition of “sentinel event” to include nonfatal adverse outcomes and near misses have changed the study results and implications?
The credibility and appeal of the Weill Cornell patient safety program to a consumer-oriented audience might have been greater had results shown a decrease, not just in sentinel events but in other more frequent and often preventable adverse obstetrical outcomes such as unnecessary major surgical procedures (Weill Cornell has an extraordinarily high, 40 percent cesarean section rate), severe perineal tears, postpartum hemorrhage, neonatal ICU admissions for sepsis and jaundice, and postpartum post-traumatic stress disorder.

 

How did the criteria for identifying sentinel events change at the hospital over the study period?
Despite systems to track errors, adverse events, and near misses, internal and external underreporting remains a significant problem in hospitals and health care facilities everywhere (citation: Drake-Land B. CMS never events: exploring the connection between tracking near misses, organizational learning and the potential to reduce the occurrence of never events in healthcare organizations. rL Solutions. Toronto. 2008). Was it only coincidence that 2008, the first year of the CMS “Never Event” policy prohibiting hospitals from billing for serious reportable events, just happened to be the same year that Weill Cornell’s sentinel event count dropped to zero?

 

What organizational system-level changes have occurred to prevent the recurrence of adverse outcomes?
As we’ve discussed in other S&S patient safety blog posts, most adverse events are not the result of freak accidents or individual fault—they are usually the end result of a chain of chronic, repeatable, low-consequence deficiencies. The Weill Cornell program included 20 changes ranging from “labor and delivery team training” to “Internet-based required reading assignments and testing,” but included no data that measured understanding, use, or effectiveness of any of these changes. Proactive, statistically rigorous approaches like failure modes and effects analysis and root cause analysis—none of which were performed here—would have helped determine the relevance, reliability, sustainability, and cost-effectiveness of the safety interventions.

 

Were there other events or changes during this time period, aside from implementation of the patient safety program, which could have contributed to the drop in compensation payments and number of reported sentinel events?
Although the authors imply that implementation of the obstetric patient safety program was the sole driver for the drastic reduction in legal costs and adverse events, there are other contributing factors and possibilities as well. Hypothetically, an aggressive legal defense strategy and a professional culture that discourages reporting could have yielded the same results. Correlation does not imply causation.

The article focused on reducing economic losses and lawsuits as a result of catastrophic events, such as infant brain damage. A comprehensive analysis of total liability claims and costs, including cases in which a patient does not die yet still experiences significant harm, may have yielded different results. As discussed in a previous S&S blog post, the open disclosure-with-offer program at the University of Michigan (full citation: Kachalia A, Kaufman S, Boothman JD, et al. Liability claims and costs before and after implementation of a medical error disclosure program. Ann Int Med 2010; 153:213-21) demonstrated compensation payment reduction without compromising ethics, transparency, or safety culture.

The Weill Cornell article is not without merit, and the authors and the institution are to be commended for what was clearly an enormous commitment of time, energy, and money to the obstetric patient safety program during the study period. Hopefully, future continuous improvement cycles will sustain these early results, spur the gathering of additional measures, lead to more refined data analysis, and ultimately yield clear and convincing patient safety outcomes.

 

[Editor's note:  As is typical when pertaining to a pointed Letter to the Editor, AJOG has also published the Weill Cornell study authors' responses to Dr. Pil's and her colleagues' letter, including their dismissal of the concern over the Weill Cornell cesarean section rate.  To read the full response, go here.]

 

Posted by:  Tricia Pil, MD

 

 

 

 

Maternal Quality Improvement , , , ,

On Our Radar…Tocophobia and its Consequences

September 26th, 2011 by avatar

The Research
Several interesting studies have recently been published in the Scandinavian journal, Acta Obstetricia et Gynecologica Scandinavica (some of which I will cover in a subsequent post)The greatest one of interest, which has garnered much media attention lately is the study about fear of childbirth which, according to researchers, has a drastic affect on increasing instrumental deliveries (51%), labor inductions (17%), and requests for elective cesarean deliveries (30%) when compared to women not suffering from this intense form of childbirth-based fear termed “tocophobia.”

The results of this relatively small study (cases=353, controls =579) out of  University Hospital in Linköping, Central Sweden, are not necessarily surprising to many of us, but reiterate what many having been talking about for decades: fear has a very real affect on the process of labor and birth.  In fact,  in the most extreme cases, tocophobia may result in avoidance of pregnancy all together.  But for our purposes, as childbirth professionals, we need to be thinking about how we approach the topic of fear pertaining to birth in our interactions with our students/patients/clients.

Take the cascade of interventions, for example: For the woman who is increasingly anxious about what will happen during labor and birth–who asks for an elective labor induction to “just get it over with,” some of the difficulties she may be most afraid of, become a self-fulfilling prophecy when her labor is complicated by the effects of labor induction (increased pain, intensity and frequency of contractions…potential negative effects of epidural analgesia when assistance with her intense pain is requested…fetal heart rate concerns…maternal blood pressure concerns…potential advancement to cesarean surgery).

Application for Childbirth Educators
Carefully and sensitively bringing up the topic of fear related to childbirth is imperative for childbirth educators:  it gives our students the opportunity to express concerns which they might otherwise keep to themselves–thinking they are “the only ones” harboring such anxiety.   It is not about inducing or encouraging fear, rather it is about presenting the opportunity and encouraging dialogue on this topic–offering positive perspectives and coping strategies that the woman/couple may not have come up with on their own.

Don’t be Afraid to Refer
In the event we find ourselves interacting with a woman whose fear pertaining to pregnancy and/or birth is deeper than that which we feel poised to handle in class (or in clinic), referring the woman locally to a trained professional adept at counseling her through this challenge becomes a must.  Tocophobia is a very real phenomena.  This study published in Clinical Obstetrics and Gynecology, 2004 (47:3) describes tocophobia as occurring in 20% of pregnancies with disabling fear occurring in 6%.

As childbirth educators and maternity care professionals, we may not have the training or skill set to appropriately handle and solve every challenge that faces an expectant woman.  And when we don’t immediately posses those skill sets, we must invite the assistance of other professionals trained to do so.  In the mean time, proactively delivering evidence-based information that empowers (rather than frightens or degrades) expectant women can go a long way toward building confidence and reducing fear.

 

 

Posted by:  Kimmelin Hull, PA, LCCE, FACCE

New Research, News about Pregnancy, Preconception Care, Research , , , , , , , ,

When Scientific Methods Fail: New Criticisms Over the Wax et al Homebirth vs. Hospital Birth Study

April 4th, 2011 by avatar

Just when one might think the controversy over the Wax et al planned homebirth vs. planned hospital birth study might be dying down, it is instead heating up again.

The American Journal of Gynecology—in which the study was originally published in September, 2010—released its April 2011 issue last Friday, full of Letters to the Editor criticizing the study.  Written by social science, epidemiology, bioethics and public health doctoral university researchers and midwives, it almost seemed as if the journal was preparing to retract the Wax article by these inclusions.  But really, they were providing the platform for the study authors to respond to the critical letters, as suggested in an excerpt from one of those responses:

“Although our findings may be unpopular in certain quarters, they result from appropriate rigorous scientific methods that have undergone appropriate peer review.”

(More on the “scientific methods” later.)

In the concluding Editor’s comment, we are told an (anonymous) independent panel of maternal fetal medicine experts convened to review the data in the Wax study—a move to theoretically decide whether or not the journal should retract the article.  The panel’s recommendations, following this analysis of the Wax et al data, were that AJOG should publish online, a full summary of the graphs for each outcome included in the study and that no retraction of the article is warranted.  (They did admit to finding ‘minor’ discrepancies in the data—but none that seemed to warrant rescinding the article altogether.)

I will say, I have to give AJOG a little credit here:  they didn’t have to print those letters.  I can only imagine how many letters in a month a large journal like that receives.  The managing and chief editors certainly could have kept all those letters to themselves, never to print a single one.  Perhaps their PR department convinced them that doing so would have created a larger fire storm than the one (still) brewing.

Coming on the heels of articles in Nature and the Lancet, which seriously called into question the conclusions of the Wax study, there has certainly been a lot of pressure on AJOG to address its decision to publish the article at all.

Medscape is also on board the debate—having already re-published the Nature article and now making available a rebuttal article from a group of researchers—including the authors of the British Columbia and Netherlands homebirth studies the Wax article incorrectly attributed and irresponsibly excluded, respectively.  This latest article, entitled Planned Home vs. Hospital Birth: A Meta-Analysis Gone Wrong, by Carl Michal, PhD, et al, was also published last Friday.

An excerpt from the Michal paper encapsulates the problem with the Wax meta-analysis:

The statistical analysis upon which this conclusion was based was deeply flawed, containing many numerical errors, improper inclusion and exclusion of studies, mischaracterization of cited works, and logical impossibilities. In addition, the software tool used for nearly two thirds of the meta-analysis calculations contains serious errors that can dramatically underestimate confidence intervals (CIs), and this resulted in at least 1 spuriously statistically significant result. Despite the publication of statements and commentaries querying the reliability of the findings, this faulty study now forms the evidentiary basis for an American College of Obstetricians and Gynecologists Committee Opinion, meaning that its results are being presented to expectant parents as the state-of-the-art in home birth safety research.

Critical analysis of the Wax study by Michal et al includes the following:
°data included in the study suggests a higher neonatal death rate (for both home and hospital births) compared to perinatal death rates.  This, of course, is not possible as neonatal deaths ought to be included in the perinatal death numbers—therefore the data here are paradoxical in nature.

°multiple numerical errors including inconsistencies in data provided in both original and supplemental source papers; incompatibilities between data from cited sources and that which is represented in the Wax study

°inconsistencies in the authors’ definitions of perinatal and neonatal mortality

°miscalculations of some odds ratios (OR) and confidence intervals (CI)—sometimes to the tune of drastic underreporting of the CI—resulting in inaccurate statistically significant positive or negative results

°inappropriate data inclusion criteria (such as that for perineal tears, in which the Wax study only included data on first and second degree tears, rather than all perineal lacerations)

°the meta-analysis spreadsheet used to calculate 13 out of the 21 outcomes contained a computational error—making all data computed with that spreadsheet incorrect

°inclusion of reference works that, themselves, have been highly criticized for statistical inaccuracies (such as the Pang et al study that included unplanned home births when it had set out to only assess planned homebirths)

°misappropriated causation:

…the discussion of causes of neonatal mortality focuses on findings from studies that were not included in the meta-analysis, including studies that mix high-risk with low-risk cases. Of the studies that are included in the meta-analysis, none associates rates of intervention with rates of neonatal mortality.

AJOG, in an attempt to rule on the debate of whether or not the data presented in the Wax study are even valid, may have just shot itself in the foot.  Since when did ‘we published an inaccurate study, and we stand by those inaccuracies’ become acceptable?

 

(see appropriate references attached to above-linked articles)

Posted by:  Kimmelin Hull, PA, LCCE

Home Birth, Metaanalyses, Research , , , , , , ,