**Core Concept**
Impetigo herpetiformis is a rare skin condition characterized by a severe, generalized pustular psoriasis that occurs during pregnancy. It requires prompt treatment to prevent complications for both the mother and the fetus.

**Why the Correct Answer is Right**
The drug of choice for impetigo herpetiformis is corticosteroids, specifically systemic corticosteroids such as prednisolone. This is because corticosteroids can rapidly reduce inflammation and prevent the progression of the condition. The use of corticosteroids in impetigo herpetiformis is critical to prevent severe complications, including fetal growth restriction and preterm labor.

**Why Each Wrong Option is Incorrect**
**Option A:** Methotrexate is a teratogenic medication and is contraindicated in pregnancy, making it an inappropriate choice for treating impetigo herpetiformis.
**Option B:** Cyclosporine is an immunosuppressive agent that can be used to treat psoriasis, but it is not the first-line treatment for impetigo herpetiformis and may have side effects that are not ideal in pregnancy.
**Option C:** Acitretin is a retinoid that is used to treat psoriasis, but it is not typically used in pregnancy due to the risk of teratogenicity.

**Clinical Pearl / High-Yield Fact**
In pregnancy, it is essential to use corticosteroids judiciously to minimize the risk of fetal growth restriction and other complications. Aiming for the lowest effective dose and duration of treatment is crucial.

**Correct Answer:** C. Prednisolone.