Most common type of phagus in twins?
**Core Concept**
Monochorionic diamniotic (MoDi) twins are a type of monochorionic twin pregnancy, where two fetuses share the same placenta but have separate amniotic sacs. This type of twinning is associated with an increased risk of fetal complications, including twin-to-twin transfusion syndrome (TTTS) and selective intrauterine growth restriction (sIUGR).
**Why the Correct Answer is Right**
The most common type of placenta shared by MoDi twins is a **monochorionic placenta with dichorionic membranes**. This is because the two fetuses develop from the same blastomere, resulting in a single chorionic sac, but they have separate amniotic sacs. The shared placenta is a result of the splitting of the embryo at a later stage in development, rather than a single fertilized egg dividing.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not a recognized type of twinning or placental arrangement.
* **Option B:** Diamniotic dichorionic (DiDi) twins have separate placentas and amniotic sacs, which is not the characteristic of MoDi twins.
* **Option C:** Monochorionic monoamniotic (MoMo) twins share both the placenta and the amniotic sac, which is not the typical arrangement of MoDi twins.
**Clinical Pearl / High-Yield Fact**
It's essential to recognize the different types of twinning and their associated risks to provide appropriate prenatal care and management.
**Correct Answer: C. Monochorionic placenta with dichorionic membranes**