MSFinals-3464

A 28-year-old woman has been diagnosed with gestational diabetes mellitus and is referred to the joint antenatal and diabetic clinic. She is currently 25 weeks pregnant and this is her first pregnancy. Her family has no history of pregnancy-related problems, but her father has type 1 diabetes mellitus. On examination, her BMI is 32 kg/m² and otherwise normal. What diagnostic test would confirm her condition?