Vascular endothelial growth factor (VEGF) in the
ovine fetal membranes appears to be a mediator of this process.
VEGF promotes blood vessel development within the amnion and
influences the permeability of the microvessels, which perfuse the
fetal and placental surfaces.7 The demonstration of aquaporin
proteins in fetal membranes suggests the possibility of water
channels as another potential regulator.