Friday, April 8, 2011

A flawed analysis

This week's leading story on Medscape OB/GYN and Women's Health []
Planned Home vs Hospital Birth: A Meta-Analysis Gone Wrong

A Flawed Analysis

The highly charged debate over the safety of home birth was inflamed by the publication of a meta-analysis by Joseph R. Wax and coworkers,[1] which concluded that "less medical intervention during planned home birth is associated with a tripling of the neonatal mortality rate." 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,[2-6] this faulty study now forms the evidentiary basis for an American College of Obstetricians and Gynecologists Committee Opinion,[7] meaning that its results are being presented to expectant parents as the state-of-the-art in home birth safety research.

In this article we describe in detail numerous mistakes in design, methodology, and reporting in the Wax meta-analysis that place clinicians and patients at risk for being misinformed.

Soon after the Wax et al article was published, the Midwives Alliance of North America published a similar critique.

Click here for the MANA press release, published by midwivesVictoria blog at the time.

Wax and colleagues were mirrored at about the same time by a similarly outrageous 2010 publication by Kennare et al in the Medical Journal of Australia.
Planned home and hospital births in South Australia, 1991-2006: differences in outcomes (MJA 2010;192:76-80)

The authors of the Australian study, which looked retrospectively at data, claimed that "planned homebirths had a perinatal mortality rate similar to that for planned hospital births, but a sevenfold higher risk of intrapartum death and a 27-fold higher risk of death from intrapartum asphyxia." Huge confidence intervals and small numbers were clear limitations, as well as decisions about inclusions and exclusions, yet the flawed conclusions have been circulated widely in a shrowd-waving "doctor knows best" campaign.

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