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Flashcards in Pathology of Twinning Deck (14)
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Types of twinning

  • Dichorionic diamnionic (amnions may be fused)
    • Monozygotic (split <3 d postconception) or dizygotic
  • Monochorionic Diamnionic (75% of twins)
    • Monozygotic
  • Monochorionic Monoamnionic
    • “MOMO”
    • Monozygotic (>8 d postconception)


Common/rates of complications with twinning

  • 3x risk for fetal anomalies (Most commonly occurs w/one umbilical artery)
  • 10% mortality rate
  • Twin-twin transfusion syndrome
  • increased maternal complications.


Common complication in monochorionic diamniotic 

  • Twin twin transfusion syndrome: abnormal sharing of fetal circulations through an arteriovenous shunt results in a disparity in fetal blood volumes
  • almost exclusively effects mono-di twins
  • Donor twin gets wee and dehydrated and anemic and pale
  • Recipient twin is engorged and plethoric
  • Abnormal cord insertion common
  • Single umbilical artery


Common complication in monochorionic monoamniotic 

  • Twintwin transfusion syndrome: less common in MoMo due to many anastomoses 
  • Up to 40% perinatal fatality from any cause


Pathophysiology of twin-twin transfusion syndrome

  • monochorionic pregnancies there are many inter-twin vascular connections that do not exist in other twin pregnancies.
  • arteries coming from one fetus can connect to veins leading to the other fetus →  imbalance
  • imbalance of blood flow between the two fetuses one baby becomes overperfused, plethoric and has polyhydramnios (the recipient twin)
  • while the donor twin becomes growth restricted, anemic and can have oligohydramnios.
  • Donor commonly known as STUCK twin (saranwrapped to the placenta) w/ anhydramnios, renal failure and IUGR


Dizygotic twin definition/characteristics

  • Dizygotic (“Fraternal”)
  • •2 ova fertilized by 2 sperm
  • •Not genetically identical
  • •~70% of spontaneous twins
  • •~95% of ART twins


Monozygotic twin definition/characteristics

  • Monozygotic (“Identical”)
  • •1 ovum fertilized by 1 sperm, fertilized oocyte divides
  • •Genetically identical
  • •~30% of spontaneous twins
  • •3-5/1000 births


Characteristics for determining chorionicity

  • Dichorionic/Diamniotic
    • -thick dividing membrane
    • -“twin peak” or “lambda” sign
  • Monochorionic/Diamniotic
    • -thin dividing membrane
    • -“T” sign


Appearance of dichorionic placentas


Appearance of monochorionic placenta


Treatment options for twin-twin transfusion syndrome

  • Reduction amniocentesis
  • microseptostomy
  • laser ablation


Characteristics of reduction amniocentesis


  • –Removal of excess fluid from recipient twin sac using needle through mom’s abdomen
  • •Up to 3L may be removed at one time
  • •Repeated every few days to weekly
  • –Usually early delivery (29-30 weeks)
  • –Survival 18-83%


Characteristics of microseptostomy

  • –Creation of hole between the babies’ sacs
    • •Fluid moves into donor twin to equalize
  • –If hole gets larger, umbilical cords may become entangled
  • –80% survival of at least one twin and 60% survival of both twins in one study


Characteristics of laser ablation

  • –Direct visualization of communicating vessels and ablation with laser
  • –Higher complication rate (15-20%)
  • –70-80% survival of at least one twin and 35% survival of both
    • •If demise of one twin, lower rate of mortality for surviving twin (35% à 7%)