A 32-year-old multigravida (G3P2) at 30 weeks of gestation is found to have gestational diabetes on routine screening. She has been on medical nutrition therapy for 4 weeks with SMBG monitoring. Her fasting glucose readings average 98–102 mg/dL and 2-hour postprandial readings average 155–165 mg/dL. She is otherwise healthy with no complications. What is the most appropriate next step?

Explanation

## Assessment of Glycemic Control **Key Point:** After 2 weeks of MNT, this patient's glucose values persistently exceed targets (fasting ≥98 mg/dL, postprandial ≥155 mg/dL), indicating inadequate glycemic control. Pharmacotherapy is now indicated. ### Current Glycemic Targets vs. Patient's Values | Parameter | Target | Patient's Average | Status | | --- | --- | --- | --- | | Fasting glucose | < 95 mg/dL | 98–102 mg/dL | **Above target** | | 2-hour postprandial | < 120 mg/dL | 155–165 mg/dL | **Well above target** | ## Pharmacotherapy Selection in Pregnancy ```mermaid flowchart TD A[GDM with inadequate glycemic control on MNT]:::outcome --> B{Preferred agent?}:::decision B -->|First-line| C[Insulin]:::action C --> D[NPH or aspart/lispro]:::action B -->|Alternative| E[Metformin or glyburide]:::action A --> F[Fasting glucose elevated]:::outcome A --> G[Postprandial glucose elevated]:::outcome F --> H[Start basal insulin NPH]:::action G --> I[Add rapid-acting insulin with meals]:::action ``` **High-Yield:** Insulin is the gold standard for GDM requiring pharmacotherapy because: - Does not cross the placenta - Extensive safety data in pregnancy - Rapid onset allows precise glycemic control - No teratogenic risk ### Why Insulin Over Metformin/Glyburide - **Metformin:** Crosses placenta; limited long-term safety data in pregnancy; second-line option - **Glyburide:** Risk of neonatal hypoglycemia; less predictable; second-line option - **Insulin:** Safest, most effective, preferred by ACOG and international guidelines ## Insulin Initiation Strategy **Clinical Pearl:** When both fasting and postprandial glucose are elevated: 1. **Start basal insulin first** (NPH 10 units at bedtime) to address fasting hyperglycemia 2. Reassess in 3–5 days 3. Add rapid-acting insulin (aspart/lispro) with meals if postprandial targets still not met NPH 10 units is a reasonable starting dose for a non-obese, insulin-naïve patient at 30 weeks gestation. **Key Point:** Fasting hyperglycemia (98–102 mg/dL) indicates the need for basal (long-acting) insulin; postprandial hyperglycemia indicates the need for prandial (rapid-acting) insulin. Starting NPH addresses the fasting component and often improves overall glycemic control.