**Core Concept**
Hyperthyroidism in pregnancy poses significant risks to both the mother and the fetus, necessitating careful management. The primary goal is to control thyroid hormone levels while minimizing the risk of adverse effects on fetal development.

**Why the Correct Answer is Right**
The safest treatment for hyperthyroidism in pregnant women is **methimazole** (also known as Tapazole). This medication works by inhibiting the synthesis of thyroid hormones, thereby reducing the production of triiodothyronine (T3) and thyroxine (T4). Methimazole is preferred over radioactive iodine (I131) due to the risk of fetal hypothyroidism and potential long-term cognitive impairment associated with I131 exposure. Additionally, methimazole has a lower risk of inducing liver damage compared to other antithyroid medications like propylthiouracil (PTU).

**Why Each Wrong Option is Incorrect**
**Option A:** Radioactive iodine (I131) is contraindicated in pregnancy due to the risk of fetal hypothyroidism and potential long-term cognitive impairment.
**Option B:** **Propylthiouracil (PTU)** is not the preferred treatment in the first trimester due to the risk of liver damage and hepatotoxicity, although it may be used in the second and third trimesters as an alternative to methimazole.
**Option C:** **Surgery** is not typically recommended for the initial management of hyperthyroidism in pregnancy, as it carries risks of complications and may not be necessary if medical therapy is effective.

**Clinical Pearl / High-Yield Fact**
In pregnant women with hyperthyroidism, it is essential to monitor thyroid hormone levels closely and adjust medication as needed to prevent fetal hyperthyroidism or hypothyroidism.

**Correct Answer:** C. Propylthiouracil (PTU)