**Core Concept:** In pregnant patients, certain antimicrobial agents may have teratogenic effects and are contraindicated. It is essential to consider the potential risks and benefits of treatment options in pregnancy.

**Why the Correct Answer is Right:** Penicillin is generally considered safe in pregnancy, with a low risk of adverse effects on the developing fetus. The answer is not A (Penicillin), as it is an appropriate antimicrobial choice for treating various infections in pregnant patients.

**Why Each Wrong Option is Incorrect:**

**Option B (Tetracycline):** Tetracycline is contraindicated in pregnancy due to its potential for causing skeletal dysplasia in the developing fetus.

**Option C (Aminoglycosides):** Aminoglycosides, including gentamicin and streptomycin, are nephrotoxic and ototoxic, increasing the risk of kidney and hearing damage in the fetus.

**Option D (Macrolides):** Macrolides, such as erythromycin, are generally safe in pregnancy, but some studies have suggested a possible association with an increased risk of congenital heart defects.

**Clinical Pearl:** When selecting antimicrobials for pregnant patients, consider the potential risks and benefits for both the patient and the developing fetus. Choose medications with minimal or no fetal teratogenic effects, such as penicillin, whenever possible.

**Correct Answer:** C (Aminoglycosides)