**Core Concept**
The management of gestational diabetes mellitus (GDM) involves a multidisciplinary approach, focusing on lifestyle modifications and pharmacological interventions to control blood glucose levels and prevent maternal and fetal complications.

**Why the Correct Answer is Right**
Treatment of GDM typically begins with lifestyle modifications, including dietary changes, increased physical activity, and weight management. Pharmacological interventions are considered when blood glucose levels remain elevated despite lifestyle modifications. Metformin and glyburide are commonly used oral antidiabetic medications in GDM, while insulin therapy may be necessary in more severe cases. The American College of Obstetricians and Gynecologists (ACOG) recommends metformin as a first-line pharmacological agent in GDM, due to its safety profile and efficacy.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a treatment approach for GDM.
**Option B:** This option is incorrect because it is too vague and does not provide a clear treatment strategy for GDM.
**Option C:** This option is incorrect because it is incomplete and does not mention the role of lifestyle modifications in the treatment of GDM.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the primary goal of GDM treatment is to achieve normoglycemia and prevent fetal macrosomia, which can lead to complications during delivery. Metformin is often preferred over glyburide due to its lower risk of hypoglycemia and its effect on improving insulin sensitivity.

**Correct Answer: A. Lifestyle modifications and metformin as first-line pharmacological agent.**