Question

Which of the following statements about multiple pregnancies is true?

• A. Fetuses of the same gender exclude dichorionicity
• B. Twin peak sign is seen in dichorionicity
• C. Thick separating membrane is a feature of monochorionic twins
• D. Chorionicity can be reliably detected only after 16 weeks of gestation

Hint:

Lambda or twin peak sign means a wedge of placenta, which means two chorions.

Answer 1

The Correct Option is B

Step 1: Understand why chorionicity matters and how it is read on ultrasound. The key sign is at the base of the dividing membrane where it meets the placenta.

Step 2: Define the twin peak sign. In dichorionic twins, placental tissue extends up into the base of the dividing membrane, creating a triangular wedge called the twin peak or lambda sign. In monochorionic twins the membrane meets the placenta at a right angle, giving the thin T sign. So option B is correct.

Step 3: Knock out the false statements. Same gender does not exclude dichorionicity, because dizygotic same sex twins exist and monozygotic twins can be dichorionic, so A is wrong. A thick dividing membrane indicates a dichorionic pregnancy (it contains two amnions and two chorions), not monochorionic, so C is wrong. Chorionicity is read most reliably in the first trimester, roughly 10 to 14 weeks, when the lambda and T signs are clearest, so D is wrong.

Step 4: Conclude. The only true statement is that the twin peak sign indicates dichorionicity.

Answer: Twin peak sign is seen in dichorionicity (Option B).