A 28-year-old primigravida at 24 weeks gestation undergoes a 75-g oral glucose tolerance test (OGTT) for gestational diabetes screening. Her fasting blood glucose is 92 mg/dL, 1-hour value is 178 mg/dL, and 2-hour value is 155 mg/dL. She is diagnosed with gestational diabetes mellitus (GDM). Regarding the management and outcomes of GDM, all of the following are TRUE EXCEPT:

Explanation

## Gestational Diabetes Mellitus (GDM) — Management & Outcomes ### Overview GDM is carbohydrate intolerance first recognized during pregnancy. It affects 2–10% of pregnancies and carries significant maternal and fetal morbidity if untreated. ### Key Maternal & Fetal Complications **Key Point:** Maternal hyperglycemia → fetal hyperglycemia → fetal hyperinsulinemia → increased fat deposition → macrosomia, neonatal hypoglycemia, and respiratory distress syndrome. **High-Yield:** Tight glycemic control in GDM reduces: - Fetal macrosomia (>4 kg) - Neonatal hypoglycemia - Preeclampsia and gestational hypertension - Cesarean delivery rates - Neonatal ICU admission ### Pharmacological Management | Agent | Status in GDM | Evidence | |-------|---------------|----------| | **Insulin** | First-line if lifestyle fails | Gold standard; crosses placenta minimally | | **Metformin** | Safe and effective | Does NOT cross placenta significantly; reduces maternal weight gain; reduces progression to T2DM postpartum | | **Sulfonylureas** | Second-line (e.g., glyburide) | Used in some centres; less evidence than metformin | | **ACE inhibitors** | Contraindicated | Teratogenic in 1st trimester; associated with fetal renal dysgenesis | | **Thiazolidinediones** | Limited data | Generally avoided due to insufficient safety data | **Key Point:** Metformin is NOT contraindicated in GDM. It is safe, effective, and increasingly used as first-line pharmacotherapy when lifestyle modification fails. It does not cross the placenta significantly and has no teratogenic effects. ### Glycemic Targets in GDM **Clinical Pearl:** ACOG and ADA recommend: - Fasting glucose: <95 mg/dL (or <90 mg/dL in some guidelines) - 1-hour postprandial: <140 mg/dL - 2-hour postprandial: <120 mg/dL ### Management Algorithm ```mermaid flowchart TD A[GDM Diagnosed]:::outcome --> B[Dietary counseling + Exercise]:::action B --> C{Glucose targets met?}:::decision C -->|Yes| D[Continue diet + SMBG]:::action C -->|No| E[Initiate Metformin or Insulin]:::action E --> F{Targets achieved?}:::decision F -->|Yes| G[Continue therapy + Monitor]:::action F -->|No| H[Intensify: Add 2nd agent or increase insulin]:::action G --> I[Delivery planning + Postpartum glucose testing]:::outcome ``` ### Why Option 2 is the Correct Answer (The Exception) **Metformin is NOT contraindicated in GDM.** It is: 1. Safe in pregnancy (Pregnancy Category B) 2. Does not cross placenta significantly 3. Reduces maternal weight gain 4. Reduces postpartum progression to Type 2 diabetes 5. Increasingly recommended as first-line pharmacotherapy The statement "Metformin is absolutely contraindicated in GDM and should never be used" is **FALSE** and is the exception. ### Why the Other Options Are Correct **Option 0 (Correct):** Maternal hyperglycemia → fetal hyperglycemia → fetal hyperinsulinemia → macrosomia, neonatal hypoglycemia, and respiratory distress. This is the classic pathophysiology of GDM. **Option 1 (Correct):** Tight glycemic control reduces preeclampsia, gestational hypertension, and other maternal complications. Multiple RCTs (e.g., MiG trial) have demonstrated this. **Option 3 (Correct):** Insulin is the gold standard therapy when lifestyle modification and dietary management fail to achieve glycemic targets. It is safe in pregnancy and does not cross the placenta. **High-Yield:** The MiG (Metformin in Gestational Diabetes) trial showed that metformin is non-inferior to insulin for GDM management and is now widely accepted as first-line pharmacotherapy.