Hiroko KONNO¹, Takeshi MURAKOSHI¹, Eri SOGA¹, Shuhei TERADA¹, Mitsuru MATSUSHITA¹, Yoshiro OTSUKI²

¹Division of Obstetrics and Perinatology, Seirei Hamamatsu General Hospital, ²Department of Pathology, Seirei Hamamatsu General Hospital

キーワード : bipartite placenta, chorionicity, monochorionic diamniotic, no anastomoses, twin pregnancy

A bipartite placenta develops in 3% of monochorionic diamniotic twin pregnancies. It initially resembles a dichorionic placenta on ultrasonography, but has one chorionic and two amniotic membranes. Almost all monochorionic diamniotic twin placentae have intertwin vascular anastomoses. Older case reports have recorded cases of bipartite placenta in monochorionic diamniotic twins, with vascular anastomoses between the two fetuses---a finding considered to be a reliable marker of a monochorionic placenta. We report two cases of monochorionic diamniotic twin pregnancies, presenting with separate placental masses, and without any intertwin vascular anastomoses. Histological examination revealed a monochorionic and diamniotic intertwin membrane, but a dye injection study in each case demonstrated a complete absence of vascular anastomoses between the two parts of the placenta.