Function of chorion 1)Exchange of metabolite portion of placenta( chorion frondosum) 2)Hormone production human chorionic gonadotropin (Hcg early indication of pregnancy)Function of Chorion 1) Exchange of metabolite: portion of placenta (Chorion frondosum) 2) Hormone production: human chorionic gonadotropin (HCG) ( Early indication of pregnancy)