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

Carl A. Michal, PhD; Patricia A. Janssen, PhD; Saraswathi Vedam, SciD; Eileen K. Hutton, PhD; Ank de Jonge, PhD


April 01, 2011

In This Article

A Faulty Computational Tool

In the methods section of the article, Wax and coworkers state that the random effects analyses were performed with "an online meta-analysis calculator from the University of Pittsburgh (" This is a mischaracterization. Visiting this Web address results in a download of a Microsoft® Word document containing an embedded spreadsheet. The file is distributed as part of an online course in epidemiology.

Close inspection of the spreadsheet (retrieved on January 28, 2011), however, reveals several serious errors within the spreadsheet. The consequences of these errors are that:

  • The CI provided most likely underestimates the true CI, often dramatically;

  • The summary OR is in general incorrect;

  • The results of the analysis can appear to provide a statistically significant positive or negative result when it should not (this has in fact occurred in Wax and colleagues' article in at least 1 outcome); and

  • The calculated results depend on the order in which the studies are entered into the spreadsheet.

These errors have been confirmed by the spreadsheet's creator.[20]Refer to the appendix for details.

This spreadsheet appears to have been used to calculate results for 13 of the 21 outcomes in the paper (the investigators fail to state whether it was used for electronic fetal monitoring, but it does appear to have been used). All of the results calculated on the basis of the spreadsheet are numerically incorrect.

The article contains at least 1 outcome for which the statistical significance of the result is incorrect as a result of using the spreadsheet. For perineal lacerations, the result of an OR of 0.76 (95% CI: 0.72-0.81) would have been an OR of 1.03 (95% CI: 0.70-1.51) if a correct computational tool had been used, and very different conclusions would be drawn for this outcome. The error in data extraction associated with this outcome does not alter the finding that the use of the spreadsheet results in the wrong conclusion being drawn. We have not attempted to reproduce most of the maternal outcome results, but we expect that similarly serious errors remain.


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