Which one of the investigation modalities can diagnose gestational diabetes in a primigravida?
**Core Concept**
Gestational diabetes mellitus (GDM) is a pregnancy complication characterized by high blood glucose levels first recognized during pregnancy. Accurate diagnosis and management of GDM are essential to prevent maternal and fetal complications.
**Why the Correct Answer is Right**
The Oral Glucose Tolerance Test (OGTT) is the gold standard for diagnosing GDM. It measures the body's ability to regulate blood glucose levels after consuming a sugary drink. The test involves fasting for 8-12 hours, followed by a 1-hour glucose challenge test, and if the result is abnormal, a 3-hour OGTT is performed. This test evaluates the insulin sensitivity and glucose metabolism of the pregnant woman.
**Why Each Wrong Option is Incorrect**
**Option A:** Fasting plasma glucose (FPG) is not sufficient for diagnosing GDM, as it may not accurately reflect the body's ability to regulate glucose levels throughout the day.
**Option B:** Hemoglobin A1c (HbA1c) is not a reliable test for diagnosing GDM, as it does not accurately reflect glucose levels during the third trimester.
**Option C:** Random blood glucose testing is not a reliable method for diagnosing GDM, as it does not provide a comprehensive picture of glucose regulation throughout the day.
**Clinical Pearl / High-Yield Fact**
The American College of Obstetricians and Gynecologists (ACOG) recommends a 75-g OGTT for diagnosing GDM in primigravidas between 24 and 28 weeks of gestation.
**Correct Answer:** C. Oral Glucose Tolerance Test (OGTT).