Wednesday, December 05, 2007

Johnson and Daviss acknowledge the validity of my criticisms

Johnson and Daviss have been forced to acknowledge the validity of my analysis of the 2005 BMJ study. They updated their website 2 weeks ago to address my specific criticisms. This is implicit recognition of the fact that comparing the homebirth rates in 2000 to out of date hospital birth studies is invalid.

According to their website Understanding Birth Better:
... Since our article was submitted for publication in 2004, the NIH has published analysis more closely comparable than was available at that time, and some have tried to use it as a comparison. While we still do not offer the comparison as a completely direct one, as it is the closest we have and the comparison is occurring regardless of our cautions, we offer the following adjustments that have to be made to provide the comparison of the CPM2000 analysis in as accurate a manner as is possible with the published NIH analysis. (my emphasis)
Finally, they are coming to grips with the central issue. Even now, though, they continue to offer disingenuous excuses for their failure to appropriately analyze the data. Consider this claim: "Since our article was submitted for publication in 2004, the NIH has published analysis more closely comparable than was available at that time". However, the relevant data was published in 2002, long before their paper was submitted (Infant Mortality Statistics from the 2000 Period Linked Birth/Infant Death Data Set, published August 29, 2002). Moreover, even before publication of the analysis, Johnson and Daviss had the raw data in their possession. They used that raw data from 2000 to calculate the rates of hospital interventions, so they were fully aware of the mortality data at all times.

As they say in politics, it's not the crime, but the cover up. Johnson and Daviss are now acknowledging that they used inappropriate data for comparison with homebirth, but claiming that the correct data was not available at that time. The relevant data was in their possession the entire time, and it was even released publically years before they made their erroneous comparisons. It is is difficult to imagine a legitimate reason why a professional statistician would deliberately use the wrong statistics for comparison when the right statistics were available and actually in his possession. It seems to me that the only possible explanation is that they knew all along that their study showed that homebirth has an increased risk of preventable neonatal death compared to hospital birth.

Johnson and Daviss also publically acknowledge that my analysis of the hospital mortality rate in the year 2000 is correct:
Thus a crude comparison of the comparable rates for non-Hispanic white >37 week babies in hospital in the year 2000 would be about 0.91 neonatal deaths/1000 live births ...
That is almost exactly the figure I reached in my analysis of the hospital data. Here is what I wrote in January of 2007in my post Johnson and Daviss study shows death rate more than double the hospital group:
Looking at the raw data we find:

2,824,196 births to white women at term (37+ weeks), see Table 2
2,602 deaths of white babies weighing more that 2500 gm see Table 6
a death rate of 0.9/1000.

The hospital neonatal death rate for white babies at term of 0.9/1000 is not corrected for congenital anomalies, pre-existing medical conditions, pregnancy complications or multiple births.
Having acknowledged the real neonatal death rate in the hospital in 2000 of 0.9/1000, they face a serious problem; their study reported a neonatal death rate at homebirth of 2.6/1000 (uncorrected for congenital anomalies, breech or twins). Once again, they resort to disingenuous and deliberately misleading claims.

Let's look at their efforts to extricate themselves from the inevitable conclusion that homebirth is not as safe as hospital birth and why those attempts are misleading and invalid. Johnson and Daviss claim:
"A crude comparison of the CPM2000 death rate to the neonatal mortality rate among U.S. Non-Hispanic White women with 37 week plus births would also require the following exclusions:

5 intrapartum deaths need to be removed as the NIH data report only on live births and thus include only neonatal deaths"
According to Johnson and Daviss (farther down the page): Intrapartum Mortality - baby who died during labour (before birth). So a true intrapartum death is one in which the baby is born without any sign of life at all, not even one pulsation of the umbilical cord. Yet if you look at the descriptions of the "intrapartum deaths" in the BMJ study, it is clear that some, if not all of them are misclassified. For example, one baby is even listed as having an initial Apgar score of 1. It is very important to understand that a baby who cannot be resuscitated is NOT an intrapartum death. Unless Johnson and Daviss can show that these babies were born and had absolutely no sign of life, and therefore never received birth certificates, we must assume that these are neonatal deaths.

Johnson and Daviss also try to exclude congenital anomalies from the homebirth group, even though they are included in the hospital birth group:
3 neonatal deaths caused by fatal birth defects need to be removed. All three of these deaths would have occurred regardless of whether the birth was planned at initiation of labour to be in hospital or at home.
If congenital anomalies are in the hospital group, they MUST be included in the homebirth group, no matter how much or why Johnson and Daviss wish to exclude them. However, their excuse for excluding them is particularly unpersuasive and disingenuous: "Had these three birth defect deaths occurred among the hospital population in the present medical culture, they would have been far more likely than not to have been induced or terminated before term." This is an absurd claim: fully 25% of the neonatal deaths in the hospital group were due to congenital anomalies. There was actually a lower rate of congenital anomalies in the homebirth group than in the hospital group, not an artificially higher rate.

Finally, they also want to exclude "1 home birth neonatal death that was among the 286 Hispanic and African-American births in the dataset. Both the death and 286 births need to be removed from the comparison as they did not fit the non-Hispanic white women category provided by the NIH." That's perfectly legitimate, but that doesn't mean that we don't need to take that death into account. It simply means that we must compare the death rate among Hispanics and African-Americans at homebirth to the same groups giving birth in the hospital.

The bottom line is that the 5 "intrapartum" deaths and the 3 congenital anomalies CANNOT be removed from the homebirth deaths. The comparable death rate is not 5 among 5,132 but 13 among 5,132 for a homebirth death rate of 2.5/1000. The homebirth death rate is almost triple that of the hospital death rate for low risk white women at term.

The Johnson and Daviss 2005 BMJ study always showed and continues to show that homebirth has a higher neonatal death rate than hospital birth. Indeed, the rate is almost 3 times higher. Johnson and Daviss deliberately and disingenuously tried to obscure that fact in the original article. They now acknowledge that they used an inappropriate comparison group, yet their explanation is completely unbelievable. They claim that the appropriate data was not available, even though it had been published 2 years before. In addition, they are now making new invalid and misleading claims in attempt to avoid the inevitable and obvious conclusion that their study showed that homebirth has an increased risk of neonatal death.


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