**Core Concept**
The stillbirth definition revolves around the gestational age and birth weight criteria, which help determine the viability of the fetus at the time of birth. A stillbirth is typically defined as the birth of a fetus that has died in the womb after a certain gestational age.

**Why the Correct Answer is Right**
The World Health Organization (WHO) defines a stillbirth as a baby born with no signs of life at or after 28 weeks of gestation, regardless of birth weight. This definition is based on the understanding that a fetus beyond 28 weeks of gestation has a high chance of survival outside the womb if it were born alive. The American College of Obstetricians and Gynecologists (ACOG) also follows a similar definition, considering a stillbirth as a baby born with no signs of life at or after 20 weeks of gestation.

**Why Each Wrong Option is Incorrect**
**Option A:** This option might be incorrect if it suggests a different gestational age or birth weight criterion for stillbirth, which would not align with the WHO or ACOG definitions.
**Option B:** This option could be incorrect if it suggests a different definition, such as birth weight or other factors, which are not the primary criteria for stillbirth.
**Option C:** This option might be incorrect if it suggests a different gestational age or birth weight criterion for stillbirth, which would not align with the WHO or ACOG definitions.

**Clinical Pearl / High-Yield Fact**
The definition of stillbirth can vary slightly between organizations, but the key factor is the gestational age beyond which a fetus is considered viable and likely to survive outside the womb if born alive.

**Correct Answer: D.**