**Core Concept**
Stillbirth is defined as fetal death occurring after a certain gestational age or weight. This definition is crucial for epidemiological and clinical purposes, allowing for accurate reporting and research on fetal mortality rates.

**Why the Correct Answer is Right**
The correct answer is based on the World Health Organization's (WHO) definition of stillbirth, which is a fetus that weighs 1000 grams or more at or after 28 weeks of gestation. This definition is widely accepted and used internationally to standardize reporting of fetal mortality rates. The weight of 1000 grams is a critical threshold, as it corresponds to a gestational age of approximately 28 weeks, when the fetus is considered viable.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because there is no widely accepted definition of stillbirth based on a specific length of gestation alone.
**Option B:** Incorrect because the definition of stillbirth is not based on the presence of any specific clinical features or symptoms.
**Option C:** Incorrect because the definition of stillbirth is not based on the method of fetal death, but rather on the gestational age or weight of the fetus.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the definition of stillbirth can vary slightly between countries and organizations, but the WHO's definition is widely accepted and used as a standard.

**Correct Answer:** D. 1000 grams