A 32-year-old primigravid woman comes to the office for a follow-up appointment at 28 weeks gestation. The patient has gestational diabetes mellitus diagnosed at 25 weeks gestation and has been managing it with dietary modification. She follows a low-carbohydrate diet and eats 3 small meals and 2 snacks daily, as recommended by her dietitian. Fasting blood glucose levels have been 110-130 mg/dL for the past 3 weeks, and most of the patient's 2-hour postprandial blood glucose levels have been >140 mg/dL. Review of systems is negative for polyuria or polydipsia. BMI is 38 kg/m². Blood pressure is 134/80 mm Hg, and pulse is 76/min. Physical examination is unremarkable. Urinalysis results are as follows:
Which of the following is the best next step in management of this patient?

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11ec25c8_da34_9ace_bc81_6fa03d664a7b_MD0003_00 This patient has gestational diabetes mellitus (GDM), which is increasingly common due to the obesity epidemic. Other risk factors include GDM in a prior pregnancy and a prior macrosomic infant. All women require screening at 24-28 weeks gestation because GDM is associated with increased risk for gestational hypertension, preeclampsia, fetal macrosomia, and cesarean delivery. Patients with risk factors benefit from earlier screening (eg, early second trimester) and rescreening at 24-28 weeks if the initial screen is negative. Patients diagnosed with GDM, such as this one, are monitored with serial blood glucose level measurements (ie, fasting and either 1- or 2-hr postprandial). Dietary modification (eg, low-carbohydrate diet, small meals with intermittent snacks) is the initial approach to management. However, patients with glucose levels consistently above the target range (ie, fasting >95 mg/dL, 1-hr >140 mg/dL, 2-hr >120 mg/dL), such as this patient, require additional pharmacotherapy because dietary modification alone has proved insufficient (Choice B). Insulin is first-line pharmacotherapy because it does not cross the placenta and dosing is easily adjustable. Oral antiglycemic medications (eg, metformin, glyburide) may be used in patients who decline insulin or have difficulty administering or adhering to insulin therapy. (Choices A and D) Canagliflozin, a sodium-glucose cotransporter-2 inhibitor, reduces blood glucose levels in patients with type 2 diabetes mellitus by increasing glucose excretion in the urine. Pioglitazone, a thiazolidinedione, improves insulin sensitivity by activating peroxisome proliferator-activated receptors. Neither is recommended in pregnancy due to possible adverse fetal effects. (Choice E) Although dietary modification and exercise are advised for patients with GDM, weight loss is not recommended due to increased risk for a small-for-gestational-age infant and possible preterm delivery. Educational objective: Patients with gestational diabetes mellitus are initially prescribed dietary modification and exercise. If dietary modification fails to produce euglycemia (ie, blood glucose levels that are consistently above the target range), insulin or oral antiglycemic medications are indicated. References: Screening, diagnosis, and management of gestational diabetes mellitus. (http://www.ncbi.nlm.nih.gov/pubmed/25884746)

A 32-Year-Old Primigravid Woman Comes to the Office for a Follow-Up