Abstract
Trophoblast fusion into the multinucleated syncytiotrophoblast (SCT) appears as an inescapable feature of placentation in mammals and other viviparous species. The trophoblast cells underlying the syncytium are considered a reservoir for the restoration of the aging peripheric structure. The transition from trophoblasts to SCTs has to be tightly regulated, and could be altered by genetic anomalies or environmental exposure. The resulting defective placental function could be one of the causes of the major placental diseases, such as preeclampsia (PE) and Intra-Uterine Growth Restriction (IUGR). This review attempts to take stock of the current knowledge about fusion mechanisms and their deregulations.