Multiple Gestation
Twins
- Amionicity/Chorionicity - Determine Type of Twins
- Di/Di - Each twin has their own sac and placenta
- Mono/Di - Each twin has their own sac, however share a placenta
- Mono/Mono - Twins share the sac and placeta
- Conjoined Twins - Type of Mono/Mono Twins that are fused together
Twin Peak or Lambda Sign = Di/Di Twins
Multiple Gestation
Di/Di Twins
- Sonographic Evidence of Di/Di Twins: Twin Peak or Lambda Sign - triangular projection of tissue between the sacs with a thicker membrane in the first trimester
- Can be Fraternal or Identical Twins - only way to differentiate sonographically is if fetal sex differ
- Most common type of Twins, lowest risk for complications
Multiple Gestation
Mono/Di Twins
- Sonographic Evidence of Mono/Di Twins: Thin membrane between the two sacs, 2 yolk sacs in the 1st trimester
- Due to a shared placenta, there is increased risk for perfusion issues such as Twin-To-Twin Transfusion Syndrome(TTTS) where one fetus receives a majority of the perfusion, and the other twin (Donor Twin) is hypoperfused
No Intertwin Membrane - Mono/Mono Twins
Multiple Gestation
Mono/Mono Twins
- Sonographic Evidence of Mono/Mono Twins: No membrane between the fetuses, one placental mass
- Least Common Type of Twins with highest risk for fetal anomalies and negative fetal outcomes
- Some complications include umbilical cord entanglement, abnormal umbilical cord placental insertion, TTTS
- Conjoined Twins are considered Mono/Mono Twins that are fused together
Multiple Gestation
Triplets and More
- Important to establish amnionicity/chorionicity as early as possible
- Increased risk of complications
4 Gestational Sacs with Twin Peak Signs