**Question:** Placenta previa is characterized by all except which of the following?

A. Increased risk of bleeding during pregnancy
B. Absence of placenta in the lower uterine segment
C. Normal placental location in the uterus
D. Absence of placental calcification on ultrasound

**Core Concept:** Placenta previa is a type of placental malposition where the placenta partially or completely covers the internal os of the uterus. It increases the risk of bleeding during pregnancy due to the proximity of the placenta to the uterine عنق الرحم (cervix).

**Why the Correct Answer is Right:** Option D is incorrect because placental calcification can occur in some cases of placenta previa. While this is a characteristic finding in normal pregnancies, it does not differentiate placenta previa from normal pregnancies as placental calcification can also be seen in other placental malpositions (e.g., placenta marginalis).

**Why Each Wrong Option is Incorrect:**

**A.** Option A is incorrect because placenta previa itself does not cause placental calcification. However, increased risk of bleeding during pregnancy is a characteristic feature of placenta previa.

**B.** Option B is incorrect because although placenta previa can be present, the placental location in the uterus is not always abnormal in placenta previa. Placenta previa can occur in various placental malpositions, not just complete absence of the placenta in the lower uterine segment.

**C.** Option C is incorrect as normal placental location in the uterus is not a defining feature of placenta previa. Placenta previa is characterized by the abnormal placement of the placenta, which is not present in a normal pregnancy.

**Clinical Pearl:** Placenta previa is a significant obstetric complication that requires careful monitoring and management to prevent severe hemorrhage during labor and delivery. In cases of placenta previa, fetal and maternal care should be tailored to minimize the risk of hemorrhage.

**Correct Answer:** D. Absence of placental calcification on ultrasound scan

**Explanation:** Placenta previa is a type of placental malposition where the placenta partially or completely covers the internal os of the uterus. This condition increases the risk of bleeding during pregnancy due to the proximity of the placenta to the cervix, which can be damaged during labor and delivery. Placental calcification (option D) is a characteristic feature of normal pregnancies and not related to placental malpositions like placenta previa. Placental calcification is not specific to placenta previa and can be seen in other placental malpositions as well.