Fetal-placental and decidual-placental units: Role of endocrine and paracrine regulations in parturition

In primates, fetal adrenal and placental steroidogenic enzymatic systems ar e complementary in a fetal-placental unit, synchronizing fetal maturation a nd myometrial activation in late gestation. Moreover, as hemochorial placen tation characterizes rodents and primates, paracrine regulations between de cidua and placenta are essential to the immunotolerance of the conceptus an d its development. Thus, the decidual-placental unit remains in a striking state of decidual quiescence throughout gestation, and the reversal of this quiescence is thought to play a key role in myometrial stimulation and the onset of parturition. A comprehensive view of the control of myometrial co ntractility, th rough the interaction of paracrine and endocrine modificati ons in late gestation, is proposed. The failure of these mechanisms underli e prematurity and the use of fetal therapy in threatened preterm labor. Cop yright (C) 2000 S. Karger AG, Basel.