How many placental barrier are present in human placenta?

Dear student 

The human placenta is allanto-chorial (the chorial placental circulation is connected with the fetal allantois), hemo-chorial, discoid, pseudo-cotyledon (the villi are grouped and incompletely separated by walls that are between them), and decidual.
Humans have a multivillous placenta with only one layer of syncytiotrophoblast bathed in maternal blood