Q. Is there an exchange of cells between the mother and the fetus through the placenta?
Under usual conditions there is no passage of cells across the placenta during gestation and the placenta has a smooth mucosa separating the richly vascularized region in contact with the mother's endometrium from the umbilical cord in contact with the fetal blood this barrier is called as placental barrier although permeable to some substances (selective permeability) the placental barrier forbids the passage of cells.