Question

Which of the following is NOT a complication of a monochorionic diamniotic (MCDA) twin pregnancy?

• A. Cord entanglement
• B. Selective fetal growth restriction (sFGR)
• C. Congenital deformities
• D. Need for first-trimester medical termination of pregnancy (MTP)

Hint:

Cord entanglement needs a shared amniotic sac — think monoamniotic, not diamniotic.

Answer 1

The Correct Option is A

Step 1: Define the chorionicity/amnionicity. A monochorionic diamniotic (MCDA) twin pregnancy has a single shared placenta (monochorionic) but two separate amniotic sacs (diamniotic), with the dividing inter-twin membrane keeping the two fetuses apart.

Step 2: Recall the complications specific to monochorionicity. Because the twins share one placenta with vascular anastomoses, MCDA pregnancies are prone to twin-to-twin transfusion syndrome (TTTS), twin anemia-polycythemia sequence (TAPS), selective fetal growth restriction (sFGR), and a higher rate of congenital/structural anomalies and deformities. Single intrauterine fetal death can also injure the co-twin.

Step 3: Identify the option requiring a shared sac. Cord entanglement occurs when the two umbilical cords intertwine within a common amniotic cavity. This needs the twins to share one sac, i.e. a monochorionic monoamniotic (MCMA) pregnancy. In an MCDA pregnancy the dividing membrane physically separates the cords, so entanglement does not occur.

Step 4: Eliminate the other options. Selective FGR (option 2) and congenital deformities (option 3) are recognised MCDA complications, so they are not the answer. First-trimester MTP (option 4) is an unrelated elective procedure, not a true complication, but it is offered as a distractor; the classic and most discriminating wrong-association in this stem is cord entanglement, which is exclusively an MCMA event.

Key fact: Cord entanglement is a feature of monochorionic monoamniotic twins, NOT of MCDA twins.