**Core Concept**
The overdistended uterus in a woman during the second trimester is a clinical presentation that requires prompt evaluation to determine the underlying cause. This condition can be associated with various complications, including preterm labor, uterine rupture, and fetal distress. The possible causes include multiple gestations, polyhydramnios, and uterine anomalies.

**Why the Correct Answer is Right**
The correct answer is likely related to the presence of multiple gestations, as this is a common cause of uterine overdistension during the second trimester. In a multiple gestation, the uterus is required to accommodate more than one fetus, leading to an increase in uterine size and potential overdistension. This can be further exacerbated by the presence of polyhydramnios, which is characterized by an excessive amount of amniotic fluid.

**Why Each Wrong Option is Incorrect**
* **Option A:** While polyhydramnios can contribute to uterine overdistension, it is typically not the primary cause in the second trimester. Polyhydramnios is more commonly associated with fetal anomalies or maternal diabetes.
* **Option B:** Uterine anomalies can indeed lead to uterine overdistension, but this is a less common cause compared to multiple gestations. Uterine anomalies may also present with other symptoms such as recurrent pregnancy loss or preterm labor.
* **Option D:** This option is not a clear cause of uterine overdistension in the second trimester. While certain maternal conditions may affect uterine size or function, they are not typically associated with overdistension in the second trimester.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the presence of an overdistended uterus in the second trimester should prompt an evaluation for multiple gestations, polyhydramnios, or uterine anomalies. The clinical history and physical examination should be thoroughly assessed to determine the underlying cause and guide further management.

**Correct Answer:** C.