**Core Concept**
The treatment of cholera in pregnant women requires careful consideration of the safety of both the mother and the fetus. Cholera is a diarrheal disease caused by Vibrio cholerae, and its management involves replacing fluids and electrolytes lost due to severe diarrhea. In pregnancy, the choice of antibiotic is crucial to prevent complications while minimizing risks to the fetus.

**Why the Correct Answer is Right**
The drug of choice for treating cholera in pregnant women is Doxycycline (Option C), an antibiotic that is effective against Vibrio cholerae. Doxycycline is a tetracycline antibiotic that inhibits protein synthesis by binding to the 30S ribosomal subunit. This mechanism of action makes it effective against a wide range of bacteria, including Vibrio cholerae. In pregnancy, Doxycycline is considered safe for short-term use, typically up to 20 weeks' gestation, due to its minimal placental transfer and low risk of teratogenic effects.

**Why Each Wrong Option is Incorrect**
**Option A:** Tetracyclines are contraindicated in the second and third trimesters due to the risk of inhibiting bone growth and causing tooth discoloration in the fetus.

**Option B:** Azithromycin is a macrolide antibiotic that can be used in pregnancy but is not the first-line treatment for cholera due to its higher cost and potential for gastrointestinal side effects.

**Clinical Pearl / High-Yield Fact**
In pregnant women with cholera, it is essential to replace fluids and electrolytes promptly to prevent dehydration and shock, which can be life-threatening to both the mother and the fetus.

**Correct Answer: C. Doxycycline**