A 28-year-old primigravida at 24 weeks of gestation presents for routine antenatal care. She is asymptomatic. Her BMI is 26 kg/m², and she has no significant past medical history. A 75-g oral glucose tolerance test (OGTT) is performed as per screening protocol. Fasting glucose is 95 mg/dL, 1-hour glucose is 178 mg/dL, and 2-hour glucose is 155 mg/dL. What is the most appropriate next step in management?