Introduction

Global childhood mortality rates in the under-5s were 44 per 1,000 live births in 2013, ranging from 2.3 in Singapore to 152.5 in Guinea-Bissau (Western sub-Saharan Africa), with rates of 4.9 per 1,000 live births in the United Kingdom (UK) (1). In England and Wales there are >5,000 deaths annually in children aged 0-19 years (2) from an estimated population of 12.9 million in this age group (3). Around 3,000 of these deaths are in infants (less than 1 year) with the majority having known serious medical conditions; such deaths are hence “expected”. Most are due to perinatal and immaturityrelated conditions, which account for around 40% of cases, followed by congenital anomalies. Many of these deaths occur in the early (less than 7 days) or late neonatal (7 to 27 days) period (2). The next most commonly affected age group is adolescents, who account for around 1,000 deaths annually, with more than half being due to external, non-natural causes (2).

Unexpected death occurring in an apparently healthy infant is termed “sudden unexpected death in infancy (SUDI)” and refers to such a presentation in an infant 7-365 days of age. According to most definitions, unexpected deaths in infants under 7 days of age are excluded from the SUDI category, and instead have been termed “sudden unexpected early neonatal death (SUEND)”. All cases of SUDI and SUEND require investigation to determine the cause of death. In England and Wales such cases are referred to Her Majesty's Coroner (HMC), who will direct a post-mortem examination by a specialist pediatric pathologist. The primary rationale of the postmortem examination, including its components and ancillary investigations, is to diagnose or exclude those natural (and non-natural) causes of death which are identifiable and to allow a specific cause of death to be provided (the specific details of the autopsy procedure are detailed in Chapter 24). Whilst many cases will subsequently be found to have died from previously unrecognized medical conditions, such as congenital anomalies or acquired natural diseases, a significant number will remain unexplained despite a complete autopsy including ancillary investigations (microbiology, virology, radiology, and metabolic studies).