**Core Concept**
A sinusoidal heart rate pattern is a specific fetal heart rate tracing characteristic of fetal distress, often associated with severe fetal anemia or hypovolemia. It is a rare but serious condition that requires prompt identification and intervention.

**Why the Correct Answer is Right**
Vasa previa is a condition where fetal blood vessels are exposed in the membranes covering the cervix, leading to potential rupture and significant fetal blood loss. This can result in severe fetal anemia, which in turn causes a sinusoidal heart rate pattern. The sinusoidal pattern is characterized by a smooth, wavy baseline, often with a loss of beat-to-beat variability. This is due to the decreased venous return and cardiac output caused by fetal anemia.

**Why Each Wrong Option is Incorrect**
**Option A:** Placenta previa is a condition where the placenta partially or completely covers the internal cervical os. While it can lead to significant bleeding and fetal distress, it is not typically associated with a sinusoidal heart rate pattern.

**Option C:** Battledore placenta, also known as a placenta marginalis, is a condition where the placenta is attached to the margin of the uterus rather than the center. This can lead to placental abruption and fetal distress, but it is not typically associated with a sinusoidal heart rate pattern.

**Option D:** Succenturiate placenta is a condition where there are multiple placental lobes, each with its own separate blood supply. While it can lead to complications, it is not typically associated with a sinusoidal heart rate pattern.

**Clinical Pearl / High-Yield Fact**
A sinusoidal heart rate pattern is a "red flag" for fetal distress, and prompt identification and intervention are crucial to prevent long-term sequelae. In cases of suspected vasa previa, an immediate cesarean section may be required to prevent fetal exsanguination.

**✓ Correct Answer: B. Vasa previa**