Abstract
Preeclampsia, one of the great obstetrical enigmas, has been described as a syndrome of theories. none of the theories explain the onset of preeclampsia in every or even most clinical scenarios. It has been described as a failure of placental invasion, an autoimmune phenomenon and a complex medical disorder. it is sometimes some of these things. This paper describes the normal process of placentation and the normal and abnormal placental signaling involved in the causation of this disorder. This theory of a preeclampsia event horizon explains the signaling pathophysiology and it's origin in local or widespread placental hypoxia that leads to the set of symptoms we define as preeclampsia. It describes the four pathways leading to this disorder and hypothesizes new testing needed to more precisely define preeclampsia and it's sequelae.