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

The lambda (twin peak) sign represents chorionic villi extending into the base of the inter-twin membrane, indicating dichorionic placentation.

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

The T-sign occurs in monochorionic-diamniotic twins because the thin membrane inserts perpendicularly into the placenta without chorionic villi filling the base.

Question 3

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

Accepted Answer

Monochorionic-diamniotic

Answer

TTTS requires vascular anastomoses within a shared monochorionic placenta, and diamniotic twins are the most common form in which it is diagnosed and treated.

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

Quintero Stage I is defined by the oligohydramnios-polyhydramnios sequence (TOPS) with the donor's bladder still visible on ultrasound.

Question 5

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

Accepted Answer

11–14 weeks

Answer

The lambda and T-signs are most reliably identified between 11 and 14 weeks, making this the optimal window for chorionicity determination.

PU - Pregnancy Ultrasound Certification Practice Test

PU - Pregnancy Ultrasound Certification Practice Test

PU Multiple Gestation Ultrasound