A 28-year-old primigravida at 24 weeks of gestation presents for routine antenatal care. She is asymptomatic. Her BMI is 29 kg/m², and she has a family history of type 2 diabetes mellitus. You perform a 75 g oral glucose tolerance test (OGTT). The fasting glucose is 95 mg/dL, 1-hour value is 185 mg/dL, and 2-hour value is 155 mg/dL. What is the most appropriate next step in management?