**Core Concept**
Betamethasone is a corticosteroid used for fetal lung maturation and prevention of respiratory distress syndrome in preterm infants. Induction of labor involves stimulating uterine contractions to initiate delivery. Various pharmacological agents can be used for this purpose, including prostaglandins and oxytocin.

**Why the Correct Answer is Right**
Betamethasone is not used for induction of labor. Instead, it is administered to pregnant women at risk of preterm delivery to accelerate fetal lung maturation. This is crucial for preventing respiratory distress syndrome in preterm infants. Betamethasone works by stimulating the production of surfactant, a substance that reduces the surface tension in the lungs, thus facilitating easier breathing. In contrast, drugs like PGE1 and PGE2 are used for induction of labor due to their ability to stimulate uterine contractions.

**Why Each Wrong Option is Incorrect**
**Option A:** PGE2 is indeed used for induction of labor, as it stimulates uterine contractions and ripening of the cervix.
**Option B:** PGE1 is also used for induction of labor, as it has a similar mechanism of action to PGE2.
**Option C:** Mifepristone is a progesterone receptor antagonist that can be used for medical termination of pregnancy, but it is not typically used for induction of labor.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that corticosteroids like betamethasone have a different role in obstetrics, focusing on fetal lung maturation and prevention of respiratory distress syndrome, whereas prostaglandins and oxytocin are used for induction of labor.

**✓ Correct Answer: D. Betamethasone**