The fetal blood is separated from syncytiotrophoblast with all the following except
The decidua over the abembryonic pole is the decidua capsularis. 
The chorionic cavity becomes larger. the decidua capsularis is stretched and degenerates.
The chorion leave now comes into close contact with the uterine wall on the opposite side, resulting in the formation of the decidua parietalis.
Fetal blood capillary membrane
Mesenchyme of intervillous blood space
Cytotrophoblast
Decidua parietalis