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What’s the right C-section rate? Higher than you think.

Editor’s Note: Dr. Mark Crislip has been kidnapped by anti-vaccinationists. Fortunately, we have sent our black Illuminati, pharma-funded, vaccine-wielding helicopters to rescue him, but unfortunately, as a result of his trauma, his usual Friday post is likely to be delayed either until this afternoon or Saturday. In any case, fortunately for us our latest addition to the SBM crew, Dr. Tuteur, was willing to fill in on short notice; so here she is. Dr. Crislip will post by tomorrow. To whet your appetite for his patented sarcasm, let me just say that he will be having a little fun with a certain article from The Atlantic about flu vaccines. There, now doesn’t that make you want to check back tomorrow to find out what his take is on the article? I thought it would.

Buried in the midst of it new report, Monitoring emergency obstetric care; a handbook, the World Health Organization acknowledges what obstetricians have been saying for some time. The WHO’s goal of a 10-15% C-section rate lacks any empirical basis.

Earlier editions of this handbook set a minimum (5%) and a maximum (15%) acceptable level for caesarean section. Although WHO has recommended since 1985 that the rate not exceed 10–15%, there is no empirical evidence for an optimum percentage or range of percentages …

Of course, they’re not going to give up their recommendation simply because there is no science that supports it, insisting that “a growing body of research that shows a negative effect of high rates.”

Dr. Marsden Wagner, former head of the Perinatal Division of the WHO, appears to be responsible for the purported optimal C-section rate of 10-15%, the level at which both maternal and neonatal mortality rates are supposedly the lowest. Ironically, Dr. Wagner is a co-author of a recent study that actually demonstrates the opposite.

The paper is Rates of caesarean section: analysis of global, regional and national estimates (Paediatric and Perinatal Epidemiology, 2007; 21:98–113.) The article explicitly acknowledges that the 15% C-section rate recommendation was made without any data to support it:

Since publication of the WHO consensus statement in 1985, debate regarding desirable levels of CS has continued; nevertheless, this paper represents the first attempt to provide a global and regional comparative analysis of national rates of caesarean delivery and their ecological correlation with other indicators of reproductive health.

The data regarding C-section rates below 10% is stark:

…[T]he majority of countries with high mortality rates have CS rates well below the recommended range of 10–15%, and in these countries there appears to be a strong ecological association between increasing CS rates and decreasing mortality.

How about the data on C-section rates above 15%? The authors claim:

Interpretation of the relationship between CS rates and mortality in countries with low mortality rates is more ambiguous; nevertheless, the sum total of the evidence presented here supports the hypothesis that, as has been argued previously, when CS rates rise substantially above 15%, risks to reproductive health outcomes may begin to outweigh benefits.

Not exactly. Indeed, not even close. The data show that low maternal mortality and low neonatal mortality are associated almost exclusively with high and very high C-section rates.

The article contains a variety of charts that make this clear. Of note, rather than graphing C-section rates against mortality rates, the authors chose to graph the log (logarithm) of C-section rates against the log of mortality rates. A log-log graph has the advantage of exposing tiny differences when all the values are bunched close together, but all the values are not bunched together in this situation. C-section rates occur along a broad range, and mortality rates occur along a broad range. As a consequence, the log-log graph magnifies the effect of tiny differences and minimizes the effect of large differences. Therefore, you need to be very careful in interpreting the graphs.

This is an adaptation of the chart that appears in the paper comparing C-section rate to maternal mortality (the authors claim that graphing C-section rate against neonatal mortality produces a similar result). The area representing a C-section rate of 10-15% has been highlighted in yellow. The horizontal blue line represents a mortality rate of 15/100,000. Lower mortality rates are below the blue line and higher mortality rates are above the blue line.

The data themselves are quite clear. There are only 2 countries in the world that have C-section rates of less than 15% AND low rates of maternal and neonatal mortality. Those countries are Croatia (14%) and Kuwait (12%). Neither country is noted for the accuracy of its health statistics. In contrast, EVERY other country in the world with a C-section rate of less than 15% has higher than acceptable levels of maternal and neonatal mortality. There nothing ambiguous about that.

The authors claim:

Although below 15% higher CS rates are unambiguously
correlated with lower maternal mortality; above this range, higher CS rates are predominantly correlated with higher maternal mortality.

No, that’s not what it shows at all. It shows that only countries with high C-section rates have low levels of maternal and neonatal mortality. A high C-section rate does not guarantee low maternal and neonatal mortality because C-section rate is not the only factor. For example, Latin America (represented on the chart by open diamonds) has a high rate of C-sections performed for social reasons, but does not have a low level of maternal mortality.

The bottom line is this: The only countries with low rates of maternal and neonatal mortality have HIGH C-section rates (except Croatia and Kuwait). The average C-section rate for countries with low maternal and neonatal mortality is 22%, although rates as high as 36% are consistent with low rates of maternal and neonatal mortality.

The authors’ claims are not supported by their own data. There is simply no support for a C-section rate of 15%, since virtually none of the countries with low rates of maternal and neonatal mortality have a C-section rate of 15% or below, and most have rates that are far higher. There is also no support for the claim that “the sum total of the evidence presented here supports the hypothesis that … when CS rates rise substantially above 15%, risks to reproductive health outcomes may begin to outweigh benefits”. When C-sections are performed for medical indications, there is no evidence that rising C-section rates lead to rising rates of maternal or neonatal mortality.

The authors own data indicate that a C-section rate of 15% is unacceptably low, and that the average should be at least 22%, with rates as high as 36% yielding low levels of maternal and neonatal mortality.

Posted in: Obstetrics & gynecology, Science and Medicine

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