Transfer of nutrients and waste products through the placental membrane that consists of cells of embryonic origin including cytotrophoblast, syncytiotrophoblast, and a fibrovascular stroma which is made of connective tissue in the villus and the endothelium of the fetal capillaries. This membrane acts as a filter and provides nutrients and oxygen from the maternal blood and allows diffusion of waste products such as carbon dioxide, bilirubin and urea. Unfortunately, this barrier also allows the passage of chemical agents such as alcohol and microorganisms such as virus of rubella, cytomegalovirus which are harmful to the fetus. Therefore, the name of placental barrier is inappropriately used to refer to the placental membrane.