Standard, Population & Customised fetal size charts 6 – practical problems with race or ethnicity

Last Saturday (click here) I suggested that the relation between race or ethnicity and poor pregnancy outcomes made customisation of fetal size charts by either, a poor way to improve detection of adverse outcomes. This post considers more practical issues.

Classification of human beings by race, an inherent physical or biological quality attributable to some groups rather than others, arose as a scientific idea in the 17th century, reached its full flowering in the 19^th, degenerated into a justification for mass murder in the mid twentieth century and is now completely discredited. Although the word “race” has a lay meaning, it no longer has a scientific one. Even if we wanted to, we couldn’t customise charts by race.

Classification by ethnic group, shared ancestry, language, homeland and other cultural features, is possible but also problematic. Definitions of what constitutes an ethnic group vary over time and by who is doing the classification, and the history of claiming ethnic differences in other areas such as IQ, criminality, sporting prowess etc. have all been based on poor science, often driven by racist ideas.

Ethnicity is also problematic because so many human beings are of mixed ethnicity. This paper (click here) nicely shows the problems. This not only makes it difficult for the clinician faced with a mixed ethnicity parent, to know which chart to use. It also causes problems for scientists drawing up ethnically-based customised charts.  How can they ensure that the people on whom their charts were derived, were of “pure” ethnicity?

In practice most ethnically customised charts are based on “self-reported ethnicity”; typically a “tick box” completed by a clerk when the patient registers. No-one knows whether the clerk based their decision on self-report, skin colour, facial features or something else.

To summarise ethnicity is poorly defined, and many of our patients are of mixed ethnicity, so even if ethnicity wasn’t also related to poor outcomes, which it is, it would be an unsuitable factor on which to either create customised charts or to decide which charts to use.

Next weight (click here)

Jim Thornton