VASCULAR ANASTOMOSES LEADING TO AMELIA AND CUTIS APLASIA IN DIZYGOTICTWIN PREGNANCY

Dichorionic placentation is observed in both monozygotic (MZ) and dizy gotic (DZ) twinning, while monochorionic placentation is unique to MZ twinning. Examinations of monochorionic twin placentas frequently reve al the presence of vascular anastomoses between the two fetal circulat ions: such anastomoses rarely occur in dichorionic placentas, Conseque ntly, abnormalities resulting from placental vascular communications a re almost exclusively observed in MZ twin pairs with monochorionic pla centas. We report opposite-sex DZ: twins in which vascular anastomoses occurred within a fused dichorionic placenta and were associated with vascular disruptions in one twin. The liveborn male twin had amelia, cutis aplasia, and XX/YY blood chimerism; the female twin died in uter o.