Sunday, June 29, 2008

Johnson and Daviss: If at first you can't trick them, try, try again.

My persistent criticism of Johnson and Daviss for their bait-and-switch in the BMJ 2005 paper is evidently having an effect. In the paper, Johnson and Daviss compared intervention rates for homebirths in 2000 with intervention rates for low risk hospital birts in 2000. Then they compared neonatal mortality rates for homebirth in 2000 with .... a bunch of out of date studies extending back 40 years. They deliberately omitted the correct comparison with neonatal mortality rates for low risk hospital birth in 2000 because that would have shown that homebirth with a CPM had a neonatal mortality rate almost triple that of hospital birth.

Since I've exposed that trick, they've searched long and hard for a new way to fool lay people. Now they're going to claim that the neonatal mortality rate for CPM attended homebirth in 2000 was lower than they said it was. They've previewed that approach on their website, and it's time to take the show on the road. Where is the show opening? Anyone who has followed this story will be able to guess the answer, the American Public Health Association Annual Meeting in October 2008. Check it out:
Neonatal mortality and prematurity: Comparison of 5,418 planned home births with full-term hospital births in the USA

Betty-Anne Daviss, MSc, RM, Midwifery Collective of Ottawa, 36 Glen Ave, Ottawa, ON K1S 2Z7, Canada and Kenneth C. Johnson, PhD, Evidence and Risk Assessment, Public Health Agency of Canada, 120 Colonnade Rd, Ottawa, ON K1A 0K9, Canada, 613 730 0282,

We compared the neonatal mortality rate among 5,418 planned homebirths attended by Certified Professional Midwives in the year 2000 (CPM2000 study) to the U.S. National Institutes of Health (NIH) neonatal mortality rate for births in hospital to U.S. non-Hispanic white women of 37 weeks plus gestation. Prematurity rates were also examined for the two populations.

Adjustments were made to ensure that the comparisons were as close as possible to comparing like with like. (my emphasis) This included removal from the CPM2000 study death rate of intrapartum mortality, 3 deaths involving lethal birth defects unlikely to have been carried to term in the hospital population, and 1 death and 286 births among African-American and Hispanic women. After making the necessary adjustments that were possible, the neonatal death rate in both datasets was just under 1 death per 1000. The premature birth rate for the NIH non-Hispanic white births in hospital was 11.3%, more than double the rate for the women who started care with Certified Professional Midwives.

Our conclusions remain unchanged from those in the original article -- the neonatal mortality rate for low risk women in North America using Certified Professional Midwives is similar to that for low risk women in hospital in the U.S., and the intervention rates are much lower. Additionally, higher prematurity is a serious concern for the care of women planning hospital births, because prematurity is associated with higher perinatal mortality and morbidity.
In the original paper, Johnson and Daviss tried to scam people by inflating the neonatal mortality rate in the hospital group. Now that the scam has been exposed, they are going to scam people by simply pretending that the homebirth group had a lower death rate than what they originally claimed.

In other words, Johnson and Daviss originally said that homebirth in 2000 had a neonatal death rate of 2.6/1000 (including congenital anomalies). Now that I've pointed out that the neonatal death rate for low risk hospital births in 2000 was 0.9/1000, they've responded: Did we say the death rate for CPM attended births in 2000 was 2.6/1000 (including congenital anomalies)? Guess what, we just discovered we were wrong. It was actually 0.9/1000. Lucky for us that we figured that out at the same time someone publicly accused us of using the wrong numbers for the hospital group in 2000. Oh, and the hospital neonatal death rate in 2000 was 0.9/1000? What an amazing coincidence!

However, we can apply the same adjustments that Johnson and Daviss applied. According to the 2000 dataset on CDC Wonder, in the group of white women, 37+ weeks, 2500+ gm, with singletons who delivered in the hospital in 2000, we find that there were 1863 deaths, of which 1001 were due to lethal congenital anomalies. That means that the neonatal death rate for hospital birth in 2000 was 0.34/1000 after we performed the EXACT SAME adjustment that Johnson and Daviss performed on the homebirth data. Now that the groups are once again comparable, the neonatal mortality rate for homebirth in 2000 is STILL almost TRIPLE the neonatal death rate for hospital birth in 2000.

Frankly, I think what Johnson and Daviss are doing is reprehensible. They've been caught trying to trick people and instead of apologizing, they've simply switched to a new way of trying to trick people. It's too late, though. The US government is now collecting statistics on homebirth with direct entry midwives and those statistics show homebirth with a DEM to have a neonatal death rate almost triple that of low risk hospital birth.

Addendum: We cannot disregard intrapartum mortality, much as Johnson and Daviss would like to do so. They write on their website:
5 intrapartum deaths need to be removed as the NIH data report only on live births and thus include only neonatal deaths.
Just because they are removed does not mean that they can be ignored. Intrapartum deaths at homebirth must be compared to intrapartum deaths at hospital birth.

At homebirth in 2000, the intrapartum death rate was astronomical, 0.92/1000. We know from other studies that the intrapartum death rate in the hospital is approximately 0.3/1000 including ALL gestational ages and ALL pregnancy complications. The intrapartum death rate for low risk women at term is vanishingly small. For example, during the years I was practicing, I worked to 2 major urban hospitals that had a combined total of approximately 75,000 deliveries. During that time, there was one low risk intrapartum death, and that death was considered a scandal resulting in an investigation and action against the personnel involved.

The bottom line is that Johnson and Daviss can "adjust" the data to their hearts' content, but those "adjustments" must also be applied to the hospital data. When both data sets are treated the same way, the conclusions remain the same. Homebirth has an increased rate of neonatal death almost triple that of hospital birth for low risk women AND homebirth has a much higher rate of intrapartum death than hospital birth.


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