**Core Concept**
Hydatidiform mole, also known as molar pregnancy, is a rare abnormal development of the placenta that occurs during pregnancy. It is characterized by an overgrowth of trophoblastic cells, leading to the formation of a mass of fluid-filled vesicles.

**Why the Correct Answer is Right**
Theca lutein cysts are a well-known complication of hydatidiform mole. This occurs due to the high levels of human chorionic gonadotropin (hCG) produced by the abnormal trophoblastic cells. hCG stimulates the ovaries, leading to excessive production of estrogen and progesterone, which in turn causes the growth of theca lutein cysts on the ovaries. These cysts are typically bilateral and can cause significant pelvic discomfort and pain.

**Why Each Wrong Option is Incorrect**
**Option A:** Follicular ovarian cysts are a common type of ovarian cyst, but they are not specifically associated with hydatidiform mole.
**Option C:** Ovarian carcinoma is a type of ovarian cancer, and while it can cause a range of symptoms, it is not directly associated with hydatidiform mole.
**Option D:** Ovarian atrophy refers to the shrinkage of the ovaries, which is not a complication of hydatidiform mole.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that theca lutein cysts can be a sign of a molar pregnancy, and patients presenting with these cysts should be evaluated for this condition. A high index of suspicion and prompt diagnosis are crucial to prevent complications.

**Correct Answer Line**
✓ Correct Answer: B. Theca lutein cysts