## Core Concept
Gestational diabetes mellitus (GDM) is a condition characterized by high blood sugar levels that are first recognized during pregnancy. It is primarily related to **insulin resistance** and **inadequate insulin secretion**. GDM usually develops in the second or third trimester.

## Why the Correct Answer is Right
The correct answer, **ketoacidosis**, is not usually seen in GDM because, despite insulin resistance, insulin levels are typically sufficient to prevent significant ketosis. The presence of insulin, even if not at optimal levels, helps to mitigate the breakdown of fat for energy, which leads to ketoacidosis. Ketoacidosis is more commonly associated with diabetic emergencies in type 1 diabetes due to absolute insulin deficiency.

## Why Each Wrong Option is Incorrect
* **Option A:** Hyperglycemia is a hallmark of GDM, making it a condition characterized by high blood glucose levels.
* **Option B:** Insulin resistance is a key pathophysiological feature of GDM. The placenta produces hormones that increase insulin resistance, making it harder for glucose to enter cells.
* **Option C:** Obesity is a significant risk factor for developing GDM. Women with obesity are more likely to have insulin resistance.

## Clinical Pearl / High-Yield Fact
A memorable point for exams is that GDM usually does not present with **ketoacidosis** due to the presence of some insulin. However, it can lead to significant **maternal and fetal complications** if not managed properly, such as macrosomia and respiratory distress syndrome.

## Correct Answer: . ketoacidosis