Gestational Diabetes (GDM)
Gestational diabetes mellitus (GDM) is diabetes diagnosed in the second or third trimester of pregnancy that was not clearly overt diabetes prior to gestation. It affects approximately 2-10% of pregnancies in the United States. Hormonal changes from the placenta cause insulin resistance; if the mother's pancreas cannot produce enough insulin to overcome this, blood glucose levels rise.
Risks and Implications
Unmanaged GDM poses significant risks to both mother and fetus:
- Fetal Macrosomia: Excess glucose crosses the placenta, causing the baby's pancreas to produce extra insulin, leading to excessive growth (large for gestational age), increasing the risk of birth trauma or the need for a C-section.
- Neonatal Hypoglycemia: After birth, the baby continues producing high levels of insulin, but is no longer receiving the mother's excess glucose, leading to dangerous low blood sugar in the newborn.
- Future Risk: Women who experience GDM have a 50% lifetime risk of developing Type 2 Diabetes.
| Test (OGTT) | Fasting Target | 1-Hour Target | 2-Hour Target |
|---|---|---|---|
| Diagnostic Thresholds | ≥ 92 mg/dL | ≥ 180 mg/dL | ≥ 153 mg/dL |
| Management Targets (ACOG) | < 95 mg/dL | < 140 mg/dL | < 120 mg/dL |
Management Strategies
Management must be strict to protect fetal development. Interventions include:
- Medical Nutrition Therapy (MNT): The primary intervention. Focus on complex carbohydrates, distributed evenly across three meals and 2-3 snacks to prevent spikes. See our Nutrition Guide.
- Physical Activity: Light to moderate exercise after meals helps utilize glucose and lower postprandial spikes.
- Pharmacotherapy: If lifestyle interventions fail to meet targets, insulin is the gold standard therapy as it does not cross the placenta. Metformin is sometimes used, but crosses the placenta and lacks long-term safety data compared to insulin.
Common Mistakes
- Cutting out all carbohydrates: Carbohydrates are necessary for fetal brain development. The goal is to choose the right types and portions, not eliminate them.
- Failing to test post-partum: A 75g OGTT should be performed 4-12 weeks postpartum to ensure glucose metabolism has returned to normal.
Frequently Asked Questions (FAQ)
- Will my baby have diabetes?
- Having GDM does not mean the baby is born with diabetes. However, they do have a higher risk of obesity and Type 2 diabetes later in life.
- Can I use a continuous glucose monitor (CGM)?
- Yes, CGMs (like the Dexcom G7) are increasingly used in GDM to catch hidden spikes and monitor overnight fasting levels. Learn more in our Technology section.
Next Step: Learn how to manage the glycemic impact of different foods using our Glycemic Load Calculator.