**Core Concept**
Expectant management of placenta previa involves careful monitoring of the patient to prevent preterm labor, bleeding, and other complications. This approach includes medications and interventions that promote fetal and maternal well-being, but excludes procedures that may compromise the pregnancy or put the mother at risk.

**Why the Correct Answer is Right**
Cervical encirclage, or cervical cerclage, is a procedure where a stitch is placed in the cervix to prevent premature dilation and preterm labor. In the context of placenta previa, expectant management aims to maintain the pregnancy as long as possible, and cervical encirclage would actually increase the risk of complications, such as excessive bleeding and cervical laceration. In contrast, other interventions like anti-D prophylaxis (to prevent RhD alloimmunization), blood transfusions (to manage anemia and bleeding), and corticosteroids (to promote fetal lung maturity) are essential components of expectant management.

**Why Each Wrong Option is Incorrect**
* **Option A:** Anti-D prophylaxis is crucial in preventing RhD alloimmunization and is an essential part of expectant management in cases of placenta previa.
* **Option C:** Blood transfusions are often necessary to manage anemia and bleeding associated with placenta previa, making this option incorrect.
* **Option D:** Corticosteroids are used to promote fetal lung maturity and are a vital component of expectant management in cases of placenta previa.

**Clinical Pearl / High-Yield Fact**
In cases of placenta previa, expectant management involves careful monitoring of the patient's condition, and the goal is to maintain the pregnancy for as long as possible without compromising the mother's or fetus's health. It's essential to recognize the signs of impending preterm labor and bleeding, and to have a plan in place for emergency situations.

**✓ Correct Answer: B. Cervical encirclage**