Leow et al (1) report the incidence of sudden, unexpected and unexplained early neonatal death in a retrospective population-based study as 0.35/10,000 live births. The authors conclude that such deaths occur more rarely than previously appreciated and as such 'extra intrusive supervision' following birth is not justified.

Although SUNC and related-death is rare, it is important to highlight aspects which may contribute to under-recognition. The natural history of SUNC is that infants who are in a state of extremis are subsequently successfully resuscitated before dying from hypoxic-ischaemic sequelae. Traditionally the cause of death is certified according to the subsequent manifestations despite the cause of collapse being unexplained. Retrospective data collection fails to identify these infants and will underestimate the incidence of such deaths. The recently published UK and German surveillance studies of sudden unexpected neonatal collapse (SUNC) within 12-24 hours of birth, reported mortality as 0.11-0.14/10,000 (2) (3) and CEMACH data confirms a rate of 0.66/10,000 for neonatal deaths in the first week where the cause was certified 'unknown' or secondary to SIDS (4).

Secondly it is increasingly recognised that many infants collapse in circumstances suggestive of accidental asphyxiation, and therefore although their deterioration is sudden and unexpected, there is a postulated explanation. Such infants accounted for around half of all those in the UK surveillance study and their contribution to unexpected deaths should not be discounted despite there being a putative clinical cause.

In addition to the mortality from SUNC, many survivors suffer longterm neurological disability. Moreover, around a third of newborns who collapse unexpectedly do so because of an underlying condition, the outcome of which may be modified by earlier identification. A growing body of literature describes a high incidence of risk factors which are common to conventional SIDS. These include prone positioning, maternal sedation and co-sleeping (2,3). For newborn infants receiving postnatal care under the responsibility of the NHS, the authors deem that 'extra intrusive supervision' is unjustified, but have not considered that sensible recommendations about easily modifiable risk factors could be applied universally to newborns however rare SUNC appears to be.

(1) Leow JY, Ward Platt MP. Sudden, unexpected and unexplained early neonatal deaths in the North of England Arch Dis Child Fetal Neonatal Ed 2011;96:F440-F442 (2) Becher JC, Bhushan SS, Lyon AJ. Unexpected collapse in apparently healthy newborns - a prospective national study of a missing cohort of neonatal deaths and near-death events. Arch Dis Child Fetal Neonatal Ed. 2011 Jun 28. [Epub ahead of print] (3) Poets A, Steinfeldt R, Poets CF. Sudden deaths and severe apparent life-threatening events in term infants within 24 hours of birth. Pediatrics. 2011;127:e869-73. (4) Dominic Acolet, CEMACH, personal communication, 2007

Conflict of Interest:

None declared

The author has read with great interest the report of Leow and Ward Platt (1), who accurately studied the incidence of sudden, unexpected and unexplained early neonatal deaths in the North of England giving an overall rate of 0.35/10,000 live births. While several works have stressed the importance of post-mortem examination in every case of suspected sudden infant death syndrome (SIDS), little, if any, attention has been given to the mandatory need to apply the same investigational protocol also in all cases of sudden perinatal unexplained death, i.e., sudden neonatal unexplained death (SNUD) and sudden intrauterine unexplained death (SIUD) (2-5). First of all, it should be underlined that there is a clear continuum between unexplained perinatal death and SIDS, as developmental abnormalities have been detected to be common to both, particularly in the cardiac conduction system and in the brainstem centers regulating vital functions. From the analysis of the conducting tissue, the following pathological findings emerged: accessory atrio-ventricular pathways, mostly Mahaim fibers, cartilaginous hypermetaplasia, abnormal resorptive degeneration, junctional islands, persistent fetal dispersion, hypoplasia of the cardiac conduction system or of the central fibrous body, splitting of the atrio-ventricular node or of the His bundle, and the Zahn node. All of these cardiac conduction findings may be isolated incidents, but they are frequently associated with autonomic nervous system alterations of the brainstem (2-5).

There is evidence to hypothesize the presence of a preexisting damage in the cardiac conduction system and brainstem of vulnerable subjects, not only in infants - newborns 0-1 month-old and infants 1-12 month-old - but also, and at a greater frequency, in fetuses(2-5). This preexisting vulnerability, if associated to a supervening pathology, such as a bronchus-pneumonic or a placental infection act as triggering phenomenon in particularly vulnerable infants and fetuses. The SIUD/SNUD/SIDS event would occur, in subjects with preexisting still quiescent and undetected abnormality in the conducting tissue and/or brainstem, when a new pathological event, itself not deadly, concurs.

REFERENCES

1. Leow JY, Ward Platt MP. Sudden, unexpected and unexplained early neonatal deaths in the North of England. Arch Dis Child Fetal Neonatal Ed 2011 Mar 11. [Epub ahead of print] 2. Matturri L, Ottaviani G, Lavezzi AM. Guidelines for neuropathologic diagnostics of perinatal unexpected loss and sudden infant death syndrome (SIDS): a technical protocol. Virchows Arch 2008;452:19-25. 3. Ottaviani G. Crib death. Sudden unexplained death of infants: the pathologist's viewpoint, Springer-Verlag, Berlin Heidelberg, Germany 2007. 4. Matturri L, Ottaviani G, Ramos SG, Rossi L. Sudden Infant Death Syndrome (SIDS): a study of cardiac conduction system. Cardiovasc Pathol 2000;9:137-45. 5. Ottaviani G, Matturri L. Histopathology of the cardiac conduction system in sudden intrauterine unexplained death. Cardiovasc Pathol 2008;17:146-55.

Conflict of Interest:

None declared