Background: The triple risk model for sudden infant death syndrome (SIDS) has been useful in understanding its pathogenesis. Risk factors for late stillbirth are well established, especially relating to maternal and fetal wellbeing.
Discussion: We propose a similar triple risk model for unexplained late stillbirth. The model proposed by us results from the interplay of three groups of factors: (1) maternal factors (such as maternal age, obesity, smoking), (2) fetal and placental factors (such as intrauterine growth retardation, placental insufficiency), and (3) a stressor (such as venocaval compression from maternal supine sleep position, sleep disordered breathing). We argue that the risk factors within each group in themselves may be insufficient to cause the death, but when they interrelate may produce a lethal combination.
Summary: Unexplained late stillbirth occurs when a fetus who is somehow vulnerable dies as a result of encountering a stressor and/or maternal condition in a combination which is lethal for them.