## **Core Concept**
Abdominal pregnancy is a rare type of ectopic pregnancy where the fertilized egg implants outside the uterus, in the abdominal cavity. This condition is associated with high morbidity and mortality due to the risk of severe hemorrhage. The pathognomonic sign is crucial for diagnosis.

## **Why the Correct Answer is Right**
The correct answer, **C. Waddell's sign**, is pathognomonic for abdominal pregnancy. Waddell's sign refers to the elicitation of pain upon gentle pressure over the uterus (or upon moving the cervix) in a woman with an abdominal pregnancy. This occurs because the abdominal pregnancy is separate from the uterus, and manipulation of the uterus does not directly affect the implantation site, but can cause pain due to irritation of surrounding structures or the peritoneum.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not correspond with the known pathognomonic signs associated with abdominal pregnancy.
- **Option B:** Similarly, this option does not accurately represent a recognized pathognomonic sign for abdominal pregnancy.
- **Option D:** This option is also incorrect as it does not align with established medical knowledge regarding diagnostic signs of abdominal pregnancy.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that abdominal pregnancy often presents with nonspecific symptoms such as abdominal pain and vaginal bleeding. A high index of suspicion is required, especially in patients with a history of pelvic inflammatory disease, previous ectopic pregnancy, or tubal surgery. Waddell's sign, while not exclusively diagnostic on its own, contributes to the clinical suspicion that leads to further diagnostic testing.

## **Correct Answer:** . **C. Waddell's sign**