Wednesday, January 03, 2007

What led up to Henci Goer's refusal to debate

It is important to remember what led up to Henci Goer's refusal to debate. Although she has always avoided debating any medical or scientific professional, she had no public policy on the matter before last week. Furthermore, she seemed eager enough when I initially questioned her on two specific occasions and responded vigorously. What changed? It turned out that over the course of several weeks she was losing no less than 3 separate "debates" on specific issues on the Lamaze site. That's when she decided to promulgate and publicly announce her decision to limit debate with me. Personally, I don't think the timing was a coincidence. On three separate issues, she could not rebut my criticism.

What were the issues?

1. The Johnson and Daviss paper

In my judgment, this is the most important of the three issues that we were discussing. The Johnson and Daviss paper is the keystone of the public debate about homebirth. Of all the papers on homebirth, it has the fewest methodological errors. Unfortunately, the findings in the paper do not justify the conclusions. That's because Johnson and Daviss deliberately chose to use the wrong comparison (cohort) group in order to make homebirth look "safe" by comparison. That's hardly suprising since the researchers were committed public advocates of homebirth, the study was commissioned by homebirth advocates and was funded by a homebirth advocacy organization.

Lamaze published a screed on its website condemning ACOG's claim that there is no scientific evidence to support the safety of homebirth. Seven different homebirth advocates contributed to this essay, and the Johnson and Daviss paper figured prominently. When I posted my criticism of the paper in response, it was ultimately Henci Goer who responded. In the next step, I provided a detailed response.
Johnson and Daviss quote a neonatal death rate at homebirth of 1.7-2/1000. The neonatal death rate in the comparable hospital group is 0.3/1000 or less. The appropriate conclusion drawn from the Johnson and Daviss data is that the neonatal death rate at homebirth is more 5 times higher than the neonatal death rate at hospital birth! Not only have Johnson and Daviss NOT shown that homebirth is as safe as hospital birth, they have actually shown that homebirth is considerably more dangerous for babies than hospital birth.
There was no response to this, no attempt at rebuttal. In support, I quoted the Rochon article on prospective cohort studies:
“Selection bias occurs when there is something inherently different between the groups being compared that could explain differences in the observed outcomes.

It is important to keep in mind the effect the choice of comparison groups will have on potential selection bias when evaluating a cohort study...
Readers should recognise the potential for selection bias in all cohort studies and carefully consider possible sources of bias..."

Selection bias is the technical term for the serious problems with the Johnson and Daviss study. Both control groups used in the study are inherently different from the homebirth group in prognostic factors including risk level, race and year of delivery. Therefore, the conclusions of the study are invalid.
That comment is not visible because it is still "in moderation" almost two weeks later.

2. The MacDorman paper

This paper purports to show that C-section increases the risk of neonatal death. Henci Goer cited it approvingly on her personal blog. I posted my criticism of the paper, in detail. The most important point is that MacDorman relied on birth certificate data that is known (from other studies) to underreport risk factors and complications. Therefore, many of the "low risk" women in the C-section group are most assuredly not low risk. Henci Goer responded with a more technical version of "it doesn't matter". Then I quoted her own words back to her:
In your essay When Research is Flawed: The Safety of Home Birth, you say:

"The study doesn't investigate whether the choice to birth at home was at fault in neonatal deaths: The investigators note that 10 of the 20 babies who died had diagnoses of congenital heart disease or respiratory distress. An additional three babies had major congenital anomalies. They do not say whether the deaths occurred at home or in hospital, nor do they speculate about how the choice of birth setting may have affected neonatal outcome in individual cases. The investigators could have reviewed the medical records on these 20 deaths, which would have provided a more accurate picture of whether home birth care affected outcome, but they did not."

So in the case of the Pang study, you thought it was quite important that the investigators actually document the connection between the cause of death and the place of birth... It is important in the interpretation of the Pang study and it is equally important in the MacDorman study. I will venture to say that you know as well as I do that C-sections did not cause the neonatal deaths in the MacDorman study.
Goer accused me of "misrepresenting" the study but could offer not even a shred of evidence on that point.

3. Goer claimed on her blog that there has been no systematic attempt to study methods of uterine closure at C-section, even though this respresents a serious issue for women attempting VBAC:
What is shocking to me is that after reading that, I tried to find studies comparing different techniques and materials with respect to scar strength and was shocked that I could not even find any randomized controlled trials, let alone a systematic review on this topic. I would have thought this was an important issue, but apparently obstetricians do not deem determining what surgical techniques produce the strongest scar a question worthy of research.
. But that's simply not true. I provided citations for 9 separate papers and then went on to say:
I just showed you studies about single vs. double layer closure. They are not the only studies of uterine scar integrity. There are studies comparing types of uterine incisions (classical vs. transverse) and there are studies investigating the results of using different suturing materials. You may not be familiar with the studies about suturing materials because many were done by infertility specialists. They have a very keen interest in minimizing any tissue reaction in surgery on the tubes or the uterus (as in the case of repair of uterine developmental defects). If you like, I can compile a list for you. The point is, though, that those studies exist and it is wrong to suggest that no one has looked into the effects of incision type, closure type and suture material on uterine scars. All three have been investigated extensively.
Not surprisingly, Goer had no comment.

So the decision to limit what I can write on her blog did not arise spontaneously. It occured in response to the fact that she could not rebut my arguments on three distinct issues. Of course she refuses to participate in a public debate of her claims. She knows she would lose, because she has already lost on 3 separate occasions.


0 Old Comments: