Reproductive: Multiple Gestations

Question 1

What are the two major categories of twins?

Answer 1

• Monozygotic (identical)
• Dizygotic (non-identical)

Question 2

What are the subtypes of monozygotic twin pregnancy?

Answer 2

• Dichorionic, diamniotic with separate placentas (split within 3 days)
• Dichorionic, diamniotic with fused placentas (split happens before 8 days)
• Monochorionic, diamniotic
• Monochorionic, monoamniotic (split happens after 8 days)
• Conjoined twins (split after 13 days)

Note: Prognosis gets worse the later the split occurs (e.g. monoamniotic twins can get tangled together).

Question 3

What are the subtypes of dizygotic twin pregnancies?

Answer 3

Dichorionic and diamniotic (this is the only option for dizygotic twins)

Question 4

How can you differentiate a monochorionic pregnancy from a dichorionic pregnancy?

Answer 4

• T sign (monochorionic) vs twin peak sign (dichorionic)
• Membrane thickness

Question 5

What type of twin pregnancy?

Answer 5

Dichorionic diamniotic

Note: Arrow point to the twin peak sign (beak-like tongue between the two membranes of a dichorionic pregnancy).

Question 6

How do some people use membrane thickness to help determine whether a pregnancy is monochorionic or not?

Answer 6

A thick, easy to see membrane (1-2 mm) is more likely to be chorion

Thin, hard to see membranes (<1 mm) are more likely to be amnion

Note: This is fairly subjective.

Question 7

What type of twin pregnancy?

Answer 7

Monochorionic diamniotic

Note: Arrow points to the intertwin membrane (T sign without twin peak sign).

Question 8

What is considered significant growth difference between twins?

Answer 8

More than 15% difference in fetal weight or abdominal circumference between twins is considered significant

Question 9

When can normal growth charts be used to evaluate twin pregnancies?

Answer 9

During the first and second trimesters

Note: During the third trimester, a different growth chart should be used.

Question 10

Twin-twin transfusion syndrome can only occur in what type of pregnancy?

Answer 10

Monochorionic twins (sharing a placenta)

Question 11

What are the complications of in utero feto-fetal transfusion?

Answer 11

• TTTS/Twin-twin transfusion syndrome (fast flow)
• TRAP/Twin reversed arterial perfusion syndrome (fast flow)
• TAPS/Twin anemia polycythemia sequence (slow flow)

Question 12

Twin-twin transfusion syndrome

Answer 12

A complication of chronic feto-fetal transfusion via a communicating vessel in the shared placenta of a monochorionic pregnancy. The majority of blood is shunted to one of the twins, resulting in a larger twin (who often gets hydrops and dies) and a skinnier twin (who actually does better).

Question 13

Twin oligohydramnios polyhydramnios sequence

Answer 13

In a monochorionic twin pregnancy, when one twin has oligohydramnios and the other has polyhdramnios. This is suspicious for twin-twin transfusion syndrome.

Question 14

Answer 14

Think twin-twin transfusion syndrome

Note: Twin A has polyhrdramnios and twin B has oligohydramnios (AKA TOPS/Twin Oligohydramnios Polyhydramnios Sequence).

Question 15

Which twin is expected to have high umbilical artery resistance in twin-twin trasnfusion syndrome?

Answer 15

The donor (skinny) twin

Question 16

Twin Reversed Arterial Perfusion Syndrome (TRAP)

Answer 16

A severe form of twin-twin transfusions syndrome, where the recipient (fat) twin gets so much extra blood that they dont develop a heart (this is the acardiac twin) and uses the other twins heart (the pump twin) to pump blood

Note: The acardiac twin will die, but the pump twin can survive as long as their heart doesn’t become strained by the extra tissue (usually this occuts if the acardiac twin is predominantly just lower extremity development).

Question 17

Doppler ultrasound demonstrates twin A umbilical artery flow oriented towards twin B…

Answer 17

Think TRAP/twin reversed arterial perfusion syndrome (Twin A is the pump twin acting as the functional heart for the acardiac twin B)

Question 18

Twin anemia polycythemia sequence

Answer 18

A syndrome related to feto-fetal transfusion in a monochorionic pregnancy where hemoglobin is transferred from one twin (that becomes anemic) to the other (which becomes polycythemic). Unlike in TTTS or TRAP, there is no oligohydramnios

Note: This often occurs after incomplete laser treatment for TTTS (twin-twin transfusion syndrome).

Question 19

Monochorionic pregnancy with discordant MCA Dopplers (evelated peak systolic velocity in twin A) s/p treatment for twin-twin transfusion syndrome…

Answer 19

Think TAPS (twin anemia polycythemia sequence) where twin A is the anemia fetus and twin B is polycythemic

Question 20

Fetus papyraceous

Answer 20

When one twin dies in utero

Note: This becomes a bigger issue for the surviving twin if it occurs later in pregnacy.

Question 21

Twin-embolization syndrome

Answer 21

Whn you have embolized, necrotic tissue embolized from a dead fetus to a living fetus. This can result in DIC, tissue ischemia, and infarction.

Note: This can only occur in a monochorionic pregnancy due to shared placental circulation.