oa Editorial [Hot topic: Sudden Unexpected Death in Infancy - Amazing Progress but Still Unanswered Questions (Guest Editor: Edwin A. Mitchell)]

The sudden unexpected death of an infant (SUDI) is one of the most tragic events that can occur to their families. The infant is seemingly healthy, probably asleep, and is then found dead. For these families the next hours and days can only be described as a nightmare. The police may investigate the case as a homicide, which causes further anguish. The families have to deal with the pathologist and coronial system (and/or medical examiner in the United States). They have to deal with their partner and the infant's brothers and sisters, who have their own needs, and with the extended family. To compound the problem many deaths are unexplained, and families are left with the unanswered question “Why did my baby die?” Their grief is overwhelming and there is guilt. It can be compounded by fear that tragedy could strike again making subsequent pregnancies and the experience of parenting fraught with anxiety. Sadly many marriages (partnerships) cannot handle these stresses, so separation and divorce is added to the trauma. Fortunately much has changed. The dramatic decline in mortality from sudden infant death syndrome (SIDS) and in total infant mortality is one of the most successful public health interventions in child health. We need to remember the pioneering work of people in the 1970s, people like Bruce Beckwith (US), John Emery (UK), Bob Carpenter (UK), Susan Beal (Australia) and Shirley Tonkin (NZ), who highlighted the problem of cot (crib) death, as it was commonly called, a problem not really recognised by hospital based paediatricians. Furthermore they made many astute clinical observations, which have been confirmed in more formal studies. The breakthrough came in the 1980s when SIDS case control studies were set up with a focus on infant care practices. The strong association with prone sleeping position was clearly seen in a number of independent studies. This led to the recommendation to avoid placing the infant to sleep in the prone position. The rest is history. Mortality declined rapidly, although some countries were late in implementing the advice and their rates remained high until they too implemented their prevention campaign. Despite the reduction in the number of babies dying, there are still many infants dying suddenly and unexpectedly. Those who die now are more likely to be from disadvantaged families, some living in poverty and chaos. These were probably always there but now are more visible because the socioeconomically advantaged families have heeded the prevention advice. This has led to deaths being labelled by pathologists as positional asphyxia, unascertained and undetermined etc. In this series we start with a discussion of the definition of SUDI and SIDS [1, 2]. We then discuss the investigation of a death with contributors describing the multidisciplinary team approach in the UK [3] and Norway [4], the role of the pathologist [5] and the death scene investigation [6]. These are best practice models of care and should be the norm. The next papers address altered physiological control during sleep [7] and potential mechanisms [8]. This is probably the hardest area of research as it is of course impossible to study living cases. One of the more exciting developments is the studying the genetics of SUDI. A small number of deaths are due to long QT syndrome [9], but many more are likely to be a combination of genetic predisposition and environmental influences [10]. We are still waiting for the first genome wide association studies (GWAS). This series (issue) has not focussed on the epidemiology of SIDS (and SUDI), as specific aspects have been reported previously. We refer readers specifically to: • Smoking [11] • Pacifiers [12, 13] • Head covering [14] • Immunisations [15] • Breastfeeding [16] One of the more contentious areas relates to the increased risk of SUDI with bed sharing. The arguments that this is a valued traditional practice and that it increases breastfeeding is balanced by the increased risk in infant death in certain circumstances....