Reclassification obscures things

EDITOR—Gardosi et al say that any classification system that results in a high proportion of cases being defined as unexplained is not fulfilling its purpose.1 If it is true, however, that the mechanism or cause leading to death in an individual case cannot be determined with more than speculative certainty, it is entirely correct to classify the case as unexplained rather than to assign a potentially erroneous or artificial cause of death in order to create the impression of knowledge.

The main finding of this study is the reclassification of numerous apparently previously unexplained cases as fetal growth restriction, such classification being on the basis of an estimated customised weight for gestation below the 10th centile. The clinical relevance of growth restriction according to these criteria remains controversial in ongoing pregnancies, and therefore to attribute the cause of death to fetal growth restriction in the absence of other specific findings may well be incorrect. It is, of course, entirely possible that growth restriction is an important contributory factor to stillbirth. However, the issue in these cases is primarily to try to understand why a minority of fetuses with mild growth restriction should die in the womb, whereas 10% of all pregnant women will show a similar degree of fetal growth restriction but will result in livebirth.

Current antenatal management detects only a small proportion of intrauterine fetal growth restriction, and improved detection methods may be associated with improved outcomes. Nevertheless, the suggestions of this study have the potential to lead to both misleading interpretations of the cause of death in future cases of stillbirth, and to a falsely inflated sense of understanding of the underlying mechanisms leading to such intrauterine death in the absence of an apparent pathophysiological basis.