What is "fetal membrane"

n. any membrane that functions for the protection or nourishment of respiration or excretion of a developing fetus

The fetal membranes are membranes associated with the developing fetus. The two chorioamniotic membranes are the amnion and chorion, which make up the amniotic sac that surrounds and protects the fetus. The other fetal membranes are the allantois and the secondary umbilical vesicle.