Module 13: Multiple Gestation Complications Flashcards
Describe the twinning stats:
1% of all pregnancies
70% dizygotic and 30% monozygotic
What increases the frequency of dizygotic twins? (4)
- Maternal age (very young and >37) and parity (++)
- Hereditary
- Racial background
- Pharmaceutical agents/ART programs
How does monozygotic twinning happen?
A single fertilized ovum replicates during the early development
What is the most important predictor of pregnancy outcome in twins?
Number of placentas
What is chorionicty and when is it best determined?
The number of placentas
Between 10 to 14 weeks LMP
What does lambda (twin peak sign) represent?
Dichorionic twinning (two placentas)
What does the T sign represent?
Monochorionic twinning (one placenta)
Only one placenta forms in what circumstance?
If the division occurs after implantation
Can dichorionic-diamniotic occur with monozygotic twins?
Yes (morula splits before it implants and each implants separately)
When does division occur with mono-di twinning?
At the blastocyst stage, day 4-8 post fertilization
When does division occur with mono-mono twinning?
At the embryonic disc stage, after the amniotic sac has formed day 8-12 post fertilization
When does division occur with conjoined twins?
Incomplete division occurs at the embryonic disc stage after day 13 post fertilization
What are two examples of abnormal twinning variations?
Conjoined twins and TRAP syndrome
Where are conjoined twins most commonly joined at?
Chest or abdomen 70% of the time (thoracopagus or omphalopagus)
What does TRAP syndrome stand for?
Twin reversed arterial perfusion
TRAP syndrome occurs with what type of twinning exclusively?
Monochorionic
What is TRAP syndrome?
A normal baby develops along with a deformed baby (only lower trunk) that steals the blood supply due to arterial-arterial or venous venous shunts in the placenta.
Why is the donor (normal) twin in TRAP syndrome at high risk for developing hydrops?
Due to high cardiac output resulting in cardiac failure
What are 5 twin complications?
- Twin to twin transfusion syndrome
- Twin embolization syndrome
- Premature delivery
- Congenital anomalies
- Cord accidents
Twin to twin transfusion syndrome occurs in what type of twinning?
Monochorionic
What is twin to twin transfusion syndrome?
Arteriovenous fistulas in the placenta(A-A, V-V or A-V), the donor becomes anemic and the recipient becomes fluid overloaded resulting in twins differing in size > 20%
Explain the recipient appearance in twin to twin transfusion syndrome:
Large, hypertensive, polyhydramnios, edematous
Explain the donor appearance in twin to twin transfusion syndrome:
Small, hypotensive, oligohydramnios, stuck twin appearance
What is a stuck twin?
In TTTS the donor twin may have little/no fluid
When does twin embolization syndrome occur?
Occurs when there is a demise of one twin clots can pass from the demise to the surviving twin resulting in infarcts in the liver and brain
What will cause asphyxia in the live surviving twin in twin embolization syndrome?
Demised twins placenta becomes a low pressure bed allowing blood to pool in the placenta (no blood pumping out due to demised fetus)
What does a papyraceous fetus mean?
Demised fetus
There is a increased risk of cord accidents in what kind of twinning?
Mono-mono
What country has a higher than average dizygotic twin rate?
Nigerian
How does dizygotic twinning happen?
Fertilization of two separate ova
What are the types of dizygotic twinning?
- DC/DA
2. DC/DA fused
What are the types of monozygotic twinning?
- DC/DA
- DC/DA fused
- MC/DA
- MC/MA
- Conjoined
How do you label twin A?
Label the presenting twin as A and label which maternal side the twin is on
What are other names for TRAP syndrome?
Acardiac parabolic twin or acardiac monster
What is fetus in fetu?
A parasitic twin resembling a teratoma within the abdomen of it’s sibling
What is superfetation?
Fertilization of two separate ova months apart
Is a stuck twin indicative of monochorionic twins?
No because a stuck twin may also occur in dichorionic twins with placenta insufficiency (IUGR)
What is the US appearance of twin embolization syndrome? (4)
- Ventriculomegaly
- Porencephalic cysts
- Cerebral atrophy
- Microcephaly
