**Core Concept**
The uterine fundus is the upper portion of the uterus, and its position and consistency are critical in assessing the uterus's postpartum recovery. After a full-term delivery, the uterus should contract and return to its pre-pregnancy size to prevent hemorrhage.

**Why the Correct Answer is Right**
Immediately after the third stage of labor, the uterus should be firm, well-contracted, and at or below the level of the umbilicus. This firmness is due to the release of oxytocin, which stimulates uterine contractions. The fundus should be palpable 1-2 cm below the umbilicus, indicating a well-contracted uterus.

**Why Each Wrong Option is Incorrect**
**Option A:** An atomic uterus is one that fails to contract properly after delivery, leading to a soft and boggy texture. This option is incorrect because an atomic uterus would not be firm or well-contracted.
**Option B:** A retroverted uterus is one where the uterus is tipped backward, but this does not affect the firmness or consistency of the uterine fundus. This option is incorrect because the question is asking about the position and consistency of the fundus, not its orientation.
**Option C:** A uterus that is palpable above the umbilicus would indicate that it has not contracted properly and is at risk for hemorrhage. This option is incorrect because the fundus should be at or below the level of the umbilicus.

**Clinical Pearl / High-Yield Fact**
A firm, well-contracted uterus is essential for preventing postpartum hemorrhage, and the fundus should be palpable 1-2 cm below the umbilicus to confirm this.

**Correct Answer:** B. The fundus of the uterus is palpable at the level of the umbilicus.