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Saturday
Apr022011

A(nother) Critique of the Wax Paper

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By ANaturalAdvocate


The Wax paper is has been all over the news recently. Not only have many discussed the paper before (see here, here, here, here, and, of course, here), but the American Journal of Obstetrics & Gynecology just posted a number of letters critical of the study, all of which are available on their website. While the editors, and a panel convened especially to review the paper at hand and available criticisms, did not feel a retraction was necessary, they did mention several concerns with the study and concluded that, “It is clear that we need more rigorous and better designed research on this important safety issue of home birth, given the many confounding factors.”

How rigorous that research might need to be is the subject of a recent Medscape article entitled “Planned Home vs Hospital Birth: A Meta-Analysis Gone Wrong.” According to the authors, there were many problems with the Wax paper and “it is incomprehensible that medical society opinion can be formulated on research that does not hold to the most basic standards of methodological rigor.”

While much of the information has been mentioned before, such as in the very comprehensive article by Gail Hart in Midwifery Today, this new critique by Michal, et al., is a much more detailed look at the methodology and analysis of the Wax paper.

Among their concerns?

  • The authors of the Wax paper included studies that did not meet the definitions of the meta-analysis itself.
  • Numerical errors significant enough that the conclusions drawn in the meta-analysis were unlikely to be accurate.
  • Instead of using widely-accepted and professional statistics software, the meta-analysis used a university class spreadsheet containing so many errors (admitted by the authors of the spreadsheet) that all of the numerical results were incorrect. Sometimes this error was significant enough that the answer reported was opposite of what the real statistics said. 
  • The meta-analysis used contradictory language in the abstract and the body of the paper itself. As many readers only can or will read the abstract of the paper, it is important that it accurately reflect the body of the paper itself.

Michal, et al., do not re-analyze the data, and do not take a position on home birth and home birth safety. However, they do recognize the “emotionally charged” atmosphere surrounding the home birth question, and state that, “Reliable information is required to allow productive debate and informed decisions.”

While a randomized study is unlikely to occur, and would be highly unwise for a number of reasons, it seems that by now accurate and appropriate analysis of the data available should not be the problem it seems to be. With home birth rates increasing, and even The Economist stepping into the fray, the need for transparent and rigorous studies is greater than ever.

 

The author very kindly thanks Christie Babinski for her assistance.

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Reader Comments (2)

I've had a look at the letters criticizing the Wax paper in the AJOG issue referenced above and also the reply of Wax and his colleagues to these criticisms (http://www.ajog.org/article/S0002-9378(11)00071-8/fulltext). The last paragraph of their reply is interesting and I had to read it several times as I couldn't quite believe what it was saying. Here it is-

"Given that the mortality rate among US term neonates without congenital anomalies is approximately 0.4/1000, a reasonable estimate of the excess neonatal mortality realized by planned home birth in this group would be 1 death per 1333 births (95% confidence interval, 1/476–1/7812). This compares favorably with the risk of a severe adverse perinatal outcome associated with a trial of labor after cesarean. However, reflexively denying the now consistently observed increased neonatal and perinatal mortality associated with planned home birth serves no conceivable good, particularly that of families choosing home birth. Considering the decreased maternal intervention, and maternal and neonatal morbidity associated with planned home birth, it remains intriguing that the most vocal criticisms of our study demonstrating the relative safety of planned home births come from birth place choice advocates."


It seems that they are now saying that their study "demonstrates the relative safety of planned home births" and therefore they don't understand why home birth advocates are criticizing it! Have I read this correctly?

April 4, 2011 | Unregistered CommenterJules

The usual way the WAX study is reported is that it showed that your baby is THREE TIMES more likely to die at home than in the hospital.

The above comment is pointing out that three times a very small number is still a very small number.

Three times .4/1000 would be 1.2/1000. 1.2-.4 = .8/1000 more babies die at home than in the hospital. Since there is no such thing as .8 of a baby, the person Jules is citing is saying that the study shows that one additional baby dies of each approximately 1333 births if the births are at home rather than in the hospital. (I didn't do this math but it seems about right.) Since everything else is better at home, isn't this an acceptable statistic, says the study's author?

Well, if 13, 330 babies were born at home in the US, that would be 10 babies that died who wouldn't have died in the hospital...which makes sufficient terrible stories to put on "Hurt by Homebirth." And for a lot of human grief. (Not that there aren't human costs to hospital birth, of course. )

Before we decide what we are willing to accept, let's please make sure the numbers are correct.

And if they are correct, lets see if there is anything we can do in terms of midwife training, and integration of home birth into the medical system to facilitate smooth transfer of care, to save some of those 10 babies. If it IS ten babies.

Susan Peterson

April 4, 2011 | Unregistered CommenterSusan Peterson
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