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The recognition of risk factors for unexpected and unexplained infants deaths (sudden infant death syndrome, (SIDS))—most importantly the risk associated with the prone sleeping position—and the implementation of risk reduction public health campaigns (eg, the ‘Back to Sleep’ campaigns in the UK in 1991 and the USA in 1994) was followed in many countries by a significant fall in the number of such deaths. In England and Wales, the overall post-neonatal mortality (PNM) rates fell in parallel with the recorded fall in SIDS, and continued to fall over the next decade, providing evidence that the fall in SIDS was not solely a consequence of diagnostic transfer.1 ,2
International comparisons of SIDS rates have been hampered by the wide variation in quality of investigation after unexpected infant deaths—particularly with regard to death-scene investigations and autopsy rates and procedures.
A further impediment to effective international comparisons has been the way in which unexpected and unexplained deaths are categorised in different jurisdictions. In the UK, the increasing use since the late 1990s of the term ‘unascertained’ rather than SIDS by some pathologists has led to further uncertainty, as these terms may translate into different International classification of Diseases, Version 10 (ICD-10) codes.3
Further uncertainty arises from the concept of how much pathology is required to fully explain an unexpected death; for instance, practising paediatricians will commonly see children who survive an illness despite radiological evidence of severe pneumonia. In …