## **Core Concept**
Rigor mortis is a well-known postmortem change characterized by muscle stiffness following death. It typically occurs within 2-4 hours after death and resolves within 18-36 hours. In the context of a fetus, the timing and occurrence of rigor mortis can provide clues about the fetal status at birth.

## **Why the Correct Answer is Right**
The correct answer involves understanding that rigor mortis in a fetus at birth can be an indicator of fetal demise or severe distress. When a fetus dies in utero, it can experience rigor mortis, which might still be present at birth. This condition suggests that the fetus had died before birth.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not provide a specific condition or timeframe related to fetal demise or birth.
- **Option B:** Similarly, this option lacks specificity regarding conditions associated with rigor mortis in a fetus at birth.
- **Option D:** This option is incorrect as it does not accurately represent a condition or scenario where rigor mortis would be relevant.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the presence of rigor mortis in a newborn can indicate **intrauterine fetal demise**. This is a critical distinction for clinicians to make, as it impacts postnatal care and parental counseling.

## **Correct Answer:** C. Intrauterine death.