## Core Concept
The core concept being tested here is the diagnosis of gestational diabetes mellitus (GDM) using the 75-gram oral glucose tolerance test (OGTT) in pregnancy. The **International Association of Diabetes and Pregnancy Study Groups (IADPSG)** criteria are commonly used for this purpose.

## Why the Correct Answer is Right
The correct answer is based on the IADPSG criteria for diagnosing GDM. According to these criteria, a fasting plasma glucose level of **≥ 92 mg/dL** is considered abnormal and suggestive of GDM. Therefore, a normal fasting plasma glucose level would be **< 92 mg/dL**. This criterion helps in early detection and management of GDM to prevent adverse pregnancy outcomes. ## Why Each Wrong Option is Incorrect - **Option A:** < 90 mg/dL - While values less than 90 mg/dL are indeed normal, the specific threshold for concern in the context of GDM diagnosis using a 75-gram OGTT is ≥ 92 mg/dL. - **Option B:** < 100 mg/dL - This is a more general criterion for impaired fasting glucose in non-pregnant individuals and does not specifically apply to the diagnosis of GDM. - **Option D:** < 110 mg/dL - This value is too high and is not used as a threshold for normal fasting glucose levels in the context of GDM screening. ## Clinical Pearl / High-Yield Fact A key point to remember is that the diagnosis of GDM can be made if one or more of the following values are met or exceeded during a 75-gram OGTT: **fasting ≥ 92 mg/dL**, **1-hour ≥ 180 mg/dL**, **2-hour ≥ 153 mg/dL**. This information is crucial for managing pregnant women at risk of GDM. ## Correct Answer: B. < 92 mg/dL.