Wednesday, January 27, 2010

Funny Figures from WHO on Caesareans

Yesterday, statistician Nigel Hawkes wrote the first journalistic article I've seen that exposes the truth about the recent WHO cesarean survey. I'm ecstatic! Writing for the website Straight Statistics, in 'Funny Figures from WHO on Caesareans', Hawkes firmly concludes:
"The findings should be ignored."

Basic premise for comparison was all wrong
Hawkes agrees with the point I made in my blog on 12 January, that (aside from the incorrect interpretation of data), using spontaneous vaginal delivery as the survey 'reference' is irrelevant. He writes:
"One final point: the comparison they make is an unfair one. The proper comparison to have made would be between women who attempt a natural birth, and women who have an elective Caesarean.
Many of those who set out to have a spontaneous birth fail, for one reason or another, and require intervention. By choosing only those who succeed and ignoring the others, the authors are failing to make their comparison on an “intention to treat” basis.

The Lancet's role in publishing the WHO's survey
Hawkes not only questions the WHO's erroneous interpretation of its own data, but also the role of the survey's reviewers. It is unclear whether he is referring to the researchers' review of their own data prior to submitting it to The Lancet, or The Lancet's review prior to accepting the text for publication, but the question he raises is valid either way:
"“The most important finding of the survey is the increased risk of maternal mortality and severe morbidity which was analysed as a composite outcome in women who undergo Caesarean section with no medical indication”, write the authors. “We conclude that Caesarean section should be done only when there is a medical indication to improve the outcome for the mother and the baby.”
Their data do not bear such a conclusion. The statistical analysis is almost certainly where the error arose. Did no referee raise the alarm?

Undeniable BiasHawkes writes: "WHO believes too many Caesareans are done without proper cause. But in interpreting these data, the authors appear to have bent over backwards to prove the point – a classic illustration of White Hat bias."

Data actually shows that cesarean delivery is safer than vaginal delivery"The records showed just 1,515 of these deliveries were by Caesarean section chosen in advance without medical indications to justify them. The vast majority (1,356) were in China; the other countries had very low numbers.
Of these 1,515 women, none died. Five were admitted to an intensive care unit (0.3 per cent) while three (0.2 per cent, though the figure published in the paper is 0.3 per cent, presumably a mathematical error) needed a blood transfusion – a total of eight out of 1,515. None required a hysterectomy.
In mothers who had vaginal deliveries, these risks were all greater: for spontaneous vaginal delivery 0.1 per cent of mothers died, 0.6 per cent were admitted to an ICU (the paper says 0.5 per cent, another miscalculation) and 1.0 per cent required a blood transfusion. A small number, 0.04 per cent, (though I make it 0.05 per cent) required a hysterectomy.

FYI (because I didn't know about it until I read this article today):-Straight Statistics is a pressure group whose aim is to detect and expose the distortion and misuse of statistical information, and identify those responsible. It has been formed by a group of legislators, statisticians and journalists, chaired by the Labour peer Lord Lipsey.

I may be accused by some as being an advocate for cesarean delivery at the expense of vaginal delivery, but the truth is, I'm an advocate of informed birth decisions, and I believe that in order for women to have access to worthwhile information in making their birth decisions, I need to continue working hard to expose the outrageous bias that exists in much of the medical and media reporting of cesarean delivery. I'm glad to have discovered today that Straight Statistics exists, and that its statisticians have confirmed my concerns about the WHO's motives.

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