It is functional stratum (sratum compactum)after implantation of blastocyst 1)DECIDUA BASALIS _PART THAT CONTRIBUTES TO MATERNAL COMPONENT OF PLACENTA IT IS FIRMLY ATTACHED TO CHORION 2)DECUDUA CAPSULARIS _PART OF ENDOMETRIUM SURROUNDS EMBRYO LIKE ACAPSULE AND SEPARATES IT FROM UTERINE CAVITY 3)DECIDUA PARIETALIS_PART OF DECIDUA THAT LINES REST OF UTERINE CAVITY FATE OF DECIDUA _as conceptus enlarges decidua capsularis enlarges into uterine cavity and finally fuses with decidua parietalis during 3rd month of pregnancy NOTE_DECIDUA IS NAMED AS SUCH (MEANING_FALLING OFF ) BECAUSE AT END OF PREGNANCY IT IS SHED OFF ALONG WITH PLACENTA AND MEMBRANES