PU Multiple Gestation Ultrasound

Question 1

Which ultrasound finding best distinguishes dichorionic-diamniotic (DCDA) twins from monochorionic-diamniotic (MCDA) twins in the first trimester?

Accepted Answer

Twin peak (lambda) sign at placental insertion

Answer

Number of yolk sacs visible

Answer

Presence of any dividing membrane

Answer

Crown-rump length discordance greater than 5 days

Question 2

The 'T-sign' on ultrasound at the placental insertion of the inter-twin membrane is associated with which type of twin placentation?

Accepted Answer

Monochorionic-diamniotic

Answer

Dichorionic-diamniotic

Answer

Monochorionic-monoamniotic

Answer

Dichorionic-monoamniotic

Question 3

Twin-to-twin transfusion syndrome (TTTS) occurs exclusively in which type of twin pregnancy?

Accepted Answer

Monochorionic-diamniotic

Answer

Dichorionic-diamniotic

Answer

Monochorionic-monoamniotic

Answer

Any dizygotic twin pregnancy

Question 4

According to the Quintero staging system for TTTS, which finding defines Stage I?

Accepted Answer

Oligohydramnios in donor and polyhydramnios in recipient with a still-visible donor bladder

Answer

Absent end-diastolic flow in the donor's umbilical artery

Answer

Hydrops in the recipient twin

Answer

Fetal demise of one twin

Question 5

At what gestational age can chorionicity be most reliably determined by ultrasound?

Accepted Answer

11–14 weeks

Answer

6–7 weeks

Answer

16–18 weeks

Answer

20–24 weeks anatomy scan

Question 6

Which ultrasound finding is most characteristic and pathognomonic of monochorionic-monoamniotic (MCMA) twins?

Accepted Answer

Umbilical cord entanglement between the twins

Answer

Lambda sign at placental insertion

Answer

Thin dividing membrane measuring less than 2 mm

Answer

Significant estimated fetal weight discordance

Question 7

In twin pregnancies, what percentage of estimated fetal weight (EFW) discordance between twins is generally considered clinically significant?

Accepted Answer

Greater than 20%

Answer

Greater than 5%

Answer

Greater than 10%

Answer

Greater than 30%