OB/GYN
Multiple Gestation & Special Twin Topics
OB/GYN

Multiple Gestation & Special Twin Topics

Chorionicity types, TTTS, MoMo twin management.

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◆Twin-twin transfusion syndrome (TTTS)

  • •Only in MCDA (shared placenta with anastomoses)
  • •Donor twin: small, anemic, oligohydramnios
  • •Recipient twin: large, polycythemic, polyhydramnios, hydrops
  • •Treatment: laser ablation of placental anastomoses

◆Complications of multiples

  • •Preterm labor (most common)
  • •Hyperemesis gravidarum (↑ β-hCG)
  • •Preeclampsia
  • •Gestational diabetes
  • •Anemia
  • •Malpresentation
  • •PPH (uterine atony from overdistention)

Twin types

TypeMechanismRisk profileDelivery
Dichorionic-diamniotic (DCDA)Dizygotic or early MZ split <3dLowest risk38 weeks
Monochorionic-diamniotic (MCDA)MZ split day 4–8TTTS risk36–37 weeks
Monochorionic-monoamniotic (MoMo)MZ split day 8–13Cord entanglement risk32–34 weeks C/S
ConjoinedMZ split day 13+VariousIndividualized

High-yield pearls

  • ◆MoMo twins: deliver C/S at 32–34 weeks (cord entanglement)
  • ◆MCDA: monitor for TTTS
  • ◆MZ split timing determines chorionicity (earlier = more separate)
  • ◆Multiples = ↑ risk of every OB complication
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