Placenta previa should be suspected in 3rd trimester in case of
**Core Concept**
Placenta previa is a condition in pregnancy where the placenta partially or completely covers the internal os of the cervix, leading to potential bleeding and complications in the third trimester. This condition is often associated with placental abruption, preterm labor, and fetal distress.
**Why the Correct Answer is Right**
The correct answer is related to the clinical presentation of placenta previa, which typically involves painless vaginal bleeding in the second or third trimester. This bleeding is usually due to the placenta separating from the uterus, leading to maternal hemorrhage. The presentation of painless vaginal bleeding in the third trimester is a classic symptom of placenta previa.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify any symptoms or signs that are typically associated with placenta previa. While abdominal pain can be a symptom of placenta previa, it is not the most characteristic or specific symptom.
**Option B:** This option is incorrect because it does not accurately describe the typical presentation of placenta previa. While vaginal bleeding can occur in the first trimester, it is less commonly associated with placenta previa.
**Option C:** This option is incorrect because it does not specify any symptoms or signs that are typically associated with placenta previa. While a low-lying placenta can be a risk factor for placenta previa, it is not a symptom of the condition.
**Clinical Pearl / High-Yield Fact**
A key clinical pearl to remember is that painless vaginal bleeding in the second or third trimester should raise suspicion for placenta previa. This symptom is often referred to as "painless vaginal bleeding" or "PVB" and is a classic presentation of this condition.
**Correct Answer:** B.