Twin placentas

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Twin placentas 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 vs. dizygotic

If no membrane between the fetuses.

  • Split at approximately 7th day.
  • Monozygotic twins.

Diamnionic-monochorionic (DiMo)

  • No interposed chorion.[1]
  • Always monozygotic.
  • Highest risk of TTTS (twin-to-twin transfusion syndrome).

Diamnionic-dichorionic (DiDi)

  • Most dizygotic (70%), may be monozygotic (30%).
  • If monozygotic -- split before 3 days.

Twin-to-twin transfusion syndrome

General

  • Abbreviated as TTTS.

Definition:

  • Monozygotic twins that share a placental disc, have vessels which cross-over between the twins that lead to a blood imbalance between the two twins.
    • Only seen in monozygotic twins.
    • Vascular connection may be vein-to-vein, artery-to-vein, artery-to-artery (uncommon).[2]

Prevalence:

  • Seen in ~15% of monozygotic twins.[2]

Clinical:

  • Donor:
    • Twin: hypovolemic, oliguric, oligohydramnic, +/- anemia, +/-hypoglycemia, +/- small pale organs.
    • Placental disc: large, pale.
  • Recipient:
    • Twin: hypervolemia, polyuria, polyhydramnios, +/- hydrops fetalis, +/- CHF, hemolytic janundice, +/- large congested organs.
    • Placental disc: small, firm, congested.

Gross

  • Large vessels that connect the two umbilical cords.

Microscopic

Features:[3]

  • Artery-to-vein anatomosis - where artery and vein are associated with different umbilical cords.
  • Donor twin side of placenta:
    • Edematous villi.
    • Increased nucleated RBCs.
  • Recipient twin side of placenta:
    • Congested.

See also

References

  1. Sternberg, Stephen S. (1997). Histology for Pathologists (2nd ed.). Lippincott Williams & Wilkins. pp. 979. ISBN 978-0397517183.
  2. 2.0 2.1 Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 469. ISBN 978-0781765275.
  3. Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 469-70. ISBN 978-0781765275.