A 28-year-old primigravida at 24 weeks of gestation undergoes routine antenatal screening and is found to have gestational diabetes mellitus (GDM). Which of the following is the most common maternal metabolic consequence of gestational diabetes?

Question

Accepted Answer

C. Insulin resistance with compensatory hyperinsulinemia. ## Pathophysiology of Gestational Diabetes

**Key Point:** Gestational diabetes is fundamentally a disorder of **insulin resistance**, not absolute insulin deficiency. The pregnant state itself induces progressive insulin resistance due to placental hormones (human placental lactogen, progesterone, cortisol).

### Mechanism of GDM Development

**High-Yield:** In normal pregnancy, insulin secretion increases to compensate for pregnancy-induced insulin resistance. When the pancreatic β-cell reserve is insufficient to maintain euglycemia despite increased insulin output, gestational diabetes develops.

1. Placental hormones (especially hPL) antagonize insulin action
2. Insulin resistance increases progressively from 2nd to 3rd trimester
3. β-cells attempt to compensate with increased secretion (hyperinsulinemia)
4. If compensation fails → fasting and postprandial hyperglycemia

### Why Other Options Are Incorrect

| Metabolic Complication | Frequency in GDM | Reason |
|---|---|---|
| **Insulin resistance + hyperinsulinemia** | **Most common** | **Fundamental pathophysiology** |
| Diabetic ketoacidosis | Rare | Requires absolute insulin deficiency; GDM patients retain β-cell function |
| Hypoglycemic episodes | Uncommon | Occurs only if insulin/sulfonylureas overdosed; not the natural metabolic state |
| Lactic acidosis | Rare | Associated with metformin in renal impairment; not a primary GDM consequence |

**Clinical Pearl:** The **fasting insulin level is elevated** in GDM even when fasting glucose is normal—this is the hallmark of insulin resistance. This distinguishes GDM from Type 1 diabetes, where insulin levels are low.

**Warning:** Do not confuse GDM with Type 1 diabetes. Type 1 presents with **insulin deficiency** (low C-peptide, positive autoantibodies); GDM presents with **insulin resistance** (high C-peptide, negative autoantibodies).

Answer

A. Diabetic ketoacidosis

Answer

B. Acute hypoglycemic episodes

Answer

D. Lactic acidosis

A 28-year-old primigravida at 24 weeks of gestation undergoes routine antenatal screening and is found to have gestational diabetes mellitus (GDM). Which of the following is the most common maternal metabolic consequence of gestational diabetes?

Explanation

Pathophysiology of Gestational Diabetes

Mechanism of GDM Development

Why Other Options Are Incorrect

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Metabolic Complication	Frequency in GDM	Reason
Insulin resistance + hyperinsulinemia	Most common	Fundamental pathophysiology
Diabetic ketoacidosis	Rare	Requires absolute insulin deficiency; GDM patients retain β-cell function
Hypoglycemic episodes	Uncommon	Occurs only if insulin/sulfonylureas overdosed; not the natural metabolic state
Lactic acidosis	Rare	Associated with metformin in renal impairment; not a primary GDM consequence