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

This post originally appeared in September 2008.

Critics the current C-section rate often quote the World Health Organization recommendation of an ideal C-section rate of 10-15%. Unfortunately, the WHO appears to have pulled those numbers out of thin air. Its own data shows that a 15% C-section rate does not result in the lowest possible levels of either neonatal mortality or maternal mortality. Indeed, Dr. Marsden Wagner, who has probably done more than anyone to promote the notion of a 15% C-section rate as ideal, is a co-author of a 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. This paper is actually the first paper that attempts to compare international C-section rates with maternal and neonatal mortality.

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, the charts are of an unusual kind. 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.

addendum: This is an adaptation of the chart that appears in the paper. The area representing a C-section rate of 10-15% has been highlighted in yellow. The vertical blue line represents a mortality rate of 15%. Lower mortality rates are left of the blue line and higher mortality rates are right of 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 all countries with high C-section rates have low levels of maternal and neonatal mortality EXCEPT Latin American countries (represented on the chart by open diamonds) with high C-section rates. The only conclusion that you can draw is that high C-section rates for medical indications are associated with low rates of maternal and neonatal mortality, and high C-section rates for social reasons (as in Latin America) do not lead to low rates of maternal and neonatal mortality.

What the data actually shows 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.

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