Which portion of the decidua does not survive until the end of pregnancy?

Answer 1

When the egg implants into the uterine wall, the decidua has three parts: decidua basalis, decidua capsularis, and decidua parietalis. Around week 22 or so of pregnancy, the decidua capsularis, which has fused with decidua parietalis, begins to lose blood supply and begins to whither away. The amniochorionic membrane also begins to develop and fuses with what is left of the decidua capsularis. When the decidua capsularis totally loses all blood supply and totally disappears, the amniochorionic membrane fuses with the decidua parietalis.