Most common type of twin pregnancy is-
**Core Concept**
The question tests the understanding of **twin pregnancy** types, which are classified based on the **placental** and **amniotic** arrangements. The most common type is determined by the **zygosity** of the twins, which can be either **monozygotic** (identical) or **dizygotic** (fraternal).
**Why the Correct Answer is Right**
The most common type of twin pregnancy is **dizygotic**, which accounts for approximately 70% of all twin pregnancies. This occurs when two separate **oocytes** are fertilized by two separate **sperm**, resulting in two genetically distinct embryos. Each embryo has its own **placenta** and **amniotic sac**, making it a **dichorionic-diamniotic** twin pregnancy.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because **monozygotic** twins, although possible, are less common than dizygotic twins.
**Option C:** Incorrect as it's not the most common type.
**Option D:** Incorrect because it is not the most frequent type of twin pregnancy.
**Clinical Pearl / High-Yield Fact**
In **dizygotic** twin pregnancies, each fetus has its own separate **placenta** and **amniotic sac**, which reduces the risk of **twin-to-twin transfusion syndrome** compared to **monozygotic** twins.
**Correct Answer:** Dizygotic twins are the most common, but the actual answer choice is not provided.