**Core Concept**
The thyroid gland plays a crucial role in pregnancy, with changes in thyroid hormone levels affecting both the mother and the fetus. During pregnancy, the thyroid gland adapts to increased demand for thyroid hormones, which are essential for fetal development.

**Why the Correct Answer is Right**
The thyroid gland increases its production of thyroid hormones, particularly triiodothyronine (T3) and thyroxine (T4), to meet the increased metabolic demands of pregnancy. This adaptation is mediated by the thyroid-stimulating hormone (TSH) produced by the pituitary gland, which stimulates the thyroid gland to release more thyroid hormones. Additionally, the thyroid gland also increases its conversion of T4 to T3, which is the more active form of thyroid hormone.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because the thyroid gland does not decrease its production of thyroid hormones during pregnancy.
**Option B:** Incorrect because the thyroid gland does not rely solely on iodine supplementation to meet the increased demand for thyroid hormones during pregnancy.
**Option C:** Incorrect because the thyroid gland does not become less sensitive to TSH during pregnancy.

**Clinical Pearl / High-Yield Fact**
It is essential for physicians to monitor thyroid function in pregnant women, especially those with a history of thyroid disease, to ensure adequate thyroid hormone levels for both the mother and the fetus.

**Correct Answer:** A.