Wednesday, April 6, 2011

Planned Home vs Hospital Birth: A Meta-Analysis Gone Wrong

That is the verbatim title of a recent article on Medscape. The entire article can be located here. It does require you to create a free account to read the article, but you will also have the opportunity to subscribe to any of there many weekly emails which can help to keep one abreast of the goings on in allopathic medicine. 

The original flawed paper by Joseph Wax et. al. is often used by homebirth opponents and was the foundation of the recent ACOG committee opinion which quoted Wax's now discredited statistic that planned homebirth carriers a two- to three- fold increase in newborn death when compared to planned hospital births.  Homebirth advocates have long been aware of many of the methodological errors. This article not only shares those concerns with a wider audience, it also points out many new faults.

Some of my favorite parts....

The authors of this months article got right down to business.

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.

This one made me LOL.

Planned Home Birth (%)Planned Hospital Birth (%)
Perinatal death
Neonatal death

Adapted from Wax JR, et al. Am J Obstet Gynecol. 2010;203:243:e1-e8.

Wax and colleagues defined perinatal death as stillbirth of at least 20 weeks or 500 g, or death of a liveborn infant within 28 days of birth. Neonatal deaths are defined as deaths of liveborn infants within 28 days of delivery.[1] With the definitions chosen by these investigators, neonatal deaths are a subset of perinatal deaths. As can be seen in Table 1, however, the investigators' results show that for planned home births, the neonatal death rates are actually far higher than the corresponding perinatal death rates. According to the investigators' definitions, these results are impossible. 

One particular study, authored by Pang was the most significant contributor to the 2-3 fold increased risk statement.  It also appears to be one of the most inappropriate studies to have been included in a meta-analysis purporting to examine the outcome of planned homebirth.

A further indication that unplanned home births are included in the study by Pang and colleagues is the fact that 7.6% of home births in that study were reported as having been attended by physicians, yet during the study period not a single physician in Washington state was known to offer home birth services [emphasis added].[22] Given that Wax and colleagues' stated goal is to compare outcomes of planned home vs planned hospital births, it is extraordinary and incomprehensible that the study by Pang and colleagues was included.

The authors of this report went back and examine the original works included in the meta- analysis as well as works they argue should have been included and weren't.  In addition to inclusion/exclusion errors and statistical analysis a large number of errors in counting were found. 

For example, we point to the study of Pang and coworkers[14] from which, to obtain results found in the summary table, the investigators must have counted 13 nonanomalous neonatal deaths in the home birth group. However, from Table 4 in that paper, it is clear that only 12 deaths should have been included.

I would urge you to read the entire critique.  It is quite damning and frankly frightening that such errors were allowed to go unchecked in such a major publication as the American Journal of Obstetrics and Gynecology


070909 Chani at the Homebirth Rights Rally, a photo by Nico Nelson on Flickr.


Lauren @ Hobo Mama said...

Thank you for going through the article so thoroughly. I remember reading various critiques of the Wax paper, but this one sounds like a wonderful addition.

Yea for home birth!

jessica said...

It was a well done critique which made reporting on much easier. I am just glad the word is getting out there regarding the flaws in the Wax study.