A 32-year-old multigravida (G3P2) from Mumbai is diagnosed with gestational diabetes at 28 weeks. She completed 2 weeks of intensive dietary counseling and home glucose monitoring (fasting 98–105 mg/dL, 2-hour postprandial 155–168 mg/dL). She is compliant with diet and exercise. What is the most appropriate pharmacological agent to initiate?

Explanation

## Pharmacotherapy for GDM: Evidence and Safety **Key Point:** When dietary intervention fails to achieve glycemic targets in GDM, **insulin is the first-line pharmacological agent** due to its proven safety record, lack of placental transfer, and extensive clinical experience in pregnancy. ## Comparison of Antidiabetic Agents in Pregnancy | Agent | Placental Transfer | Fetal Risk | Status in GDM | | --- | --- | --- | --- | | Insulin | Minimal (large molecule) | None established | **Gold standard** | | Metformin | Minimal | Generally safe; emerging evidence | Increasingly used; not first-line | | Glyburide | Minimal | Neonatal hypoglycemia risk | Avoid; associated with worse outcomes | | Sulfonylureas | Minimal | Neonatal hypoglycemia | Contraindicated | | DPP-4 inhibitors (sitagliptin) | Unknown | Limited data; not recommended | Avoid in pregnancy | | GLP-1 agonists | Unknown | Limited data | Avoid in pregnancy | **High-Yield:** The **Metformin in Gestational Diabetes (MiG) trial** (2008) showed metformin is non-inferior to insulin for GDM, but insulin remains the preferred first-line agent in most guidelines because it has the longest safety record and most robust evidence in pregnancy. ## Insulin Regimens in GDM ```mermaid flowchart TD A[GDM requires insulin]:::outcome --> B[Choose insulin type]:::decision B -->|Basal-bolus| C[NPH + rapid-acting before meals]:::action B -->|Basal only| D[NPH once or twice daily]:::action C --> E[Titrate based on SMBG]:::action D --> E E --> F[Target: fasting <95, postprandial <140 mg/dL]:::outcome ``` **Clinical Pearl:** Human NPH insulin and rapid-acting analogs (lispro, aspart) are preferred. Insulin glargine and detemir are increasingly used as basal agents. The dose typically starts at 0.3–0.5 units/kg/day and is titrated weekly based on SMBG patterns. **Warning:** Glyburide (glibenclamide) was once used in GDM but is now discouraged in many countries due to association with higher neonatal hypoglycemia and worse maternal outcomes compared to insulin in randomized trials. [cite:ACOG Practice Bulletin 190; MiG Trial Lancet 2008; NICE NG3]