A 26-year-old pregnant woman at 26 weeks gestation is undergoing a 1-hour glucose challenge screening. She drinks the 50-gram glucose solution, and her blood glucose is measured 1 hour later at 150 mg/dL. Which of the following is the most appropriate next step?

A. Repeating the screening test is not standard practice. A screening value above the threshold requires a diagnostic test, not a repeat screening. B. The 1-hour 50-gram glucose challenge is a screening test for gestational diabetes mellitus (GDM). A blood glucose level of ≥140 mg/dL (some guidelines use 130 mg/dL) indicates a positive screen. The next step is a 3-hour, 100-gram OGTT, which is the diagnostic test to confirm or rule out GDM. C. Initiating insulin therapy is premature. Diagnosis of GDM requires confirmation by the 3-hour OGTT. Treatment decisions, including diet, exercise, or insulin therapy, are based on confirmed diagnosis and blood glucose patterns. D. A 1-hour glucose level of 150 mg/dL exceeds the normal screening threshold, so further diagnostic testing is required. Reassuring without follow-up could miss a diagnosis of GDM, increasing maternal and fetal risks.