## **Core Concept**
Presumptive signs of pregnancy are those that suggest the possibility of pregnancy but are not definitive. They can be physiological, subjective, or anatomical changes that may occur during early pregnancy.

## **Why the Correct Answer is Right**
The correct answer, **C. Amenorrhea**, is a presumptive sign of pregnancy. Amenorrhea, or the absence of menstruation, is one of the earliest and most common presumptive signs of pregnancy. However, it can also be caused by other factors such as stress, hormonal imbalances, or certain medical conditions. Other presumptive signs include nausea, vomiting, and breast tenderness.

## **Why Each Wrong Option is Incorrect**
* **Option A:** While an **increase in breast size** can be a sign of pregnancy, it is not as universally recognized as a presumptive sign as amenorrhea. Breast changes can also occur due to hormonal fluctuations not related to pregnancy.
* **Option B:** **Goodell's sign**, which refers to the softening of the cervix, is a presumptive sign of pregnancy but is not as commonly cited or as easily assessed as amenorrhea.
* **Option D:** **Chadwick's sign**, which is the bluish discoloration of the vagina and cervix due to increased blood flow, is another presumptive sign. However, like Goodell's sign, it is not as straightforward or commonly used as amenorrhea for initial assessment.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that while amenorrhea is a critical presumptive sign of pregnancy, it is essential to confirm pregnancy with a definitive sign, such as a positive pregnancy test (detecting beta-hCG) or ultrasound visualization of the fetus.

## **Correct Answer: C. Amenorrhea**