Editor—The Office for National Statistics uses an algorithm to classify neonatal deaths.1It is based on an hierarchical classification of causes to derive a single cause group for each death.2 Cause groups include, in descending order: congenital malformations, antepartum infection, immaturity related conditions, asphyxia/anoxia/trauma, external conditions, infections, other specific conditions, sudden infant deaths, and other unclassified conditions.

In applying …