Uses of mortality statistics (cont.)
Defining death
It might seem odd that it is important to define ‘death’ – for most people the notion is unambiguous and obvious. However, advances in medical care have meant that it is possible for someone to be physically alive and ‘brain-dead’ or, conversely, to be mentally functional but kept alive only by means of artificial intervention (e.g. a ventilator, or life-support system). However, if one is to collect and tabulate accurate and meaningful data on vital events in a population, a clear-cut definition of death is required to avoid any such ambiguity. The definition adopted by the United Nations Statistics Division (United Nations 2001: 10 
) in conjunction with the World Health Organization is "the permanent disappearance of all evidence of life at any time after live birth has taken place (post-natal cessation of vital functions without capability of resuscitation)".
The same publication provides an extended definition of what is meant by a ‘live birth’, though that need not detain us here. What is important though is the idea that one cannot die until one has been born or until there has been permanent disappearance of all evidence of life.
All forms of prenatal, or foetal, mortality are excluded from this definition, irrespective of cause – since according to this definition, one cannot die prior to having lived. Again, the same publication offers a statistical definition of what is meant by foetal mortality, incorporating the popular terms of miscarriage, still birth, or termination of pregnancy. Statistics on foetal mortality are typically categorised by gestational age (that is, age since conception).