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(→Monozygotic vs. dizygotic: fix sp.) |
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'''Twin [[placenta]]s''' often come to the pathologist... even if they are normal. In these specimens, usually, the chorion is the key; the pathologist may be able to sort-out whether the twins are monozygotic (identical) or dizygotic (fraternal). | '''Twin [[placenta]]s''' often come to the pathologist... even if they are normal. In these specimens, usually, the chorion is the key; the pathologist may be able to sort-out whether the twins are monozygotic (identical) or dizygotic (fraternal). | ||
=Monozygotic versus dizygotic twins= | |||
==Monoamniotic-monochorionic (MoMo)== | |||
*No membrane between the fetuses. | *No membrane between the fetuses - apparently clinically. | ||
*Split at approximately 7th day. | *Split at approximately 7th day. | ||
*Monozygotic twins. | *Monozygotic twins. | ||
==Diamniotic-monochorionic (DiMo)== | |||
===General=== | |||
*Always monozygotic. | |||
*Highest risk of TTTS ([[twin-to-twin transfusion syndrome]]). | |||
===Gross=== | |||
*Thin membrane at T-zone. | |||
===Microscopic=== | |||
Features: | |||
*No interposed chorion.<ref name=Ref_H4P2_979>{{Ref H4P2|979}}</ref> | *No interposed chorion.<ref name=Ref_H4P2_979>{{Ref H4P2|979}}</ref> | ||
==Diamniotic-dichorionic (DiDi)== | |||
===General=== | |||
*Most dizygotic (70%), may be monozygotic (30%). | *Most dizygotic (70%), may be monozygotic (30%). | ||
*If monozygotic -- split before 3 days. | *If monozygotic -- split before 3 days. | ||
===Gross=== | |||
*Thick membrane at T-zone. | |||
===Microscopic=== | |||
Features: | |||
*Interposed chorion.<ref name=Ref_H4P2_979>{{Ref H4P2|979}}</ref> | |||
=Pathology seen only in twin pregnancies= | |||
==Twin-to-twin transfusion syndrome== | ==Twin-to-twin transfusion syndrome== | ||
===General=== | ===General=== | ||