Wednesday, November 14, 2007

Homebirth statistics

For those on other boards who are currently discussing the validity of homebirth studies that CLAIM to show that homebirth is as safe as hospital birth, you should consider several important point:

1. In order for a scientific paper to demonstrate that homebirth is as safe as hospital birth, it MUST compare homebirth to hospital birth in the SAME year, for women of the SAME risk. It is invalid (and sneaky) to attempt to make homebirth look good by comparing it to hospital births that include premature babies and medical complications or to compare it to hospital births in the past when neonatal mortality rates were higher.

For more information on the specifics of the Johnson and Daviss study, you can read Johnson and Daviss study shows death rate more than double the hospital group. To sum it up, according to the BMJ paper when Johnson and Daviss looked at intervention rates:

"We compared medical intervention rates for the planned home births with data from birth certificates for all 3 360 868 singleton, vertex births at 37 weeks or more gestation in the United States in 2000, as reported by the National Center for Health Statistics."

What was the neonatal death rate in that group? They don't tell you, and that's not suprising because the neonatal death rate for babies of low risk women was 0.9 per thousand, lower than the neonatal death rate at homebirth. Instead they compare the homebirth death rate to a bunch of out of date studies extending back as far as 1969.

2. You need to be aware of the conflicts of interest that exist. Johnson and Daviss, authors of the 2005 BMJ study that was the largest study of homebirth to date, are NOT independent researchers. In the paper, Johnson describes his professional position as "senior epidemiologist, Surveillance and Risk Assessment Division, Centre for Chronic Disease Prevention and Control, Public Health Agency of Canada", but he neglected to mention that he holds another position: head of the MANA Statistics and Research Committee. In fact, Johnson and Daviss have been passionate homebirth advocates for many years, long before they embarked on the study. Daviss, who is Johnson's wife, is a homebirth midwife. Furthermore, the study was not funded by an academic institution or a government agency. Rather, it was funded by Foundation for the Advancement of Midwifery, a homebirth advocacy group.

So using money from a homebirth advocacy group, NARM, a homebirth advocacy group, hired homebirth advocates Johnson and Daviss to produce a study on homebirth. The conclusion appears to be predetermined. When an industry hires known allies to do a study about that industry, the results are going to be favorable.

3. You need to consider how the scientific article was critiqued by others. For example, many homebirth advocates cite the Janssen article in support of homebirth. What they don't realize is that shortly after it was published, Janssen was forced to publicly acknowledge that her study did NOT show homebirth to be as safe as hospital birth. You can read more here: Janssen says her study does not show homebirth is as safe as hospital birth. The key points were an acknowledgement that the homebirth group differed from the hospital birth group in important ways, and that the study never even attempted to show that homebirth is as safe as hospital birth: "The purpose of our study was not to determine which method of care was better, home vs. hospital, but rather to assess whether, at the 2-year interval, home birth was safe enough to continue to be offered as a choice for women in the context of ongoing evaluation."

If you have any questions about the studies, or need clarification, don't hesitate to ask.

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