Diaphragm in sudden unexpected infant and fetal death

This commentary discusses the diaphragm hypothesis in the context of extensive neuropathological and cardiovascular investigations performed at the Lino Rossi Research Center, University of Milan, over more than two decades. These studies demonstrated that both sudden infant death syndrome (SIDS) and sudden intrauterine unexplained death (SIUD) frequently share congenital abnormalities involving the autonomic nervous system and cardiac conduction system, supporting the concept of a common prenatal developmental disorder affecting vital autonomic regulation. The diaphragm hypothesis may explain a subset of SIDS cases characterized by respiratory vulnerability; however, it appears less applicable to SIUD, since fetal survival does not depend on pulmonary ventilation. In our series, diaphragmatic tissue analysis revealed no significant abnormalities in most SIDS and SIUD cases, apart from a single SIUD case showing focal diaphragmatic hypoplasia. Current evidence suggests that SIDS is best interpreted through an integrated multifactorial model in which diaphragmatic dysfunction may contribute as one component among developmental, autonomic, genetic, and environmental factors.