Gestational Diabetes

Gestational diabetes mellitus (GDM) is diabetes that develops during pregnancy — typically in the second or third trimester — in women who did not have diabetes before becoming pregnant. It affects approximately 6–9% of all pregnancies in the United States and requires careful management to protect both mother and baby.

What Causes Gestational Diabetes?

During pregnancy, the placenta produces hormones that can block insulin's normal action — a phenomenon called insulin resistance. Most pregnant women can produce enough extra insulin to compensate. When they cannot, blood sugar rises above normal, resulting in gestational diabetes. Risk is higher in women who are overweight, have a family history of diabetes, are over age 25, or have had GDM in a previous pregnancy.

Screening and Diagnosis

All pregnant women are routinely screened between 24 and 28 weeks of pregnancy using a glucose challenge test (GCT). If the initial screen is abnormal, a 3-hour oral glucose tolerance test (OGTT) is performed. Women with significant risk factors may be screened earlier.

Risks If Untreated

Uncontrolled gestational diabetes poses risks for both mother and baby:

• For the baby: Macrosomia (large birth weight), low blood sugar at birth (neonatal hypoglycemia), premature birth, higher lifetime risk of obesity and type 2 diabetes
• For the mother: Preeclampsia, C-section delivery, and significantly increased risk of developing type 2 diabetes after pregnancy (50% within 10 years)

Management

Most women with GDM can manage blood sugar effectively through:

• Medical nutrition therapy (MNT): A carbohydrate-controlled meal plan developed with a registered dietitian
• Regular physical activity: Walking after meals significantly helps lower postmeal blood sugar
• Blood sugar monitoring: Checking fasting and post-meal glucose levels daily at home
• Insulin therapy: Required in approximately 15–30% of cases when blood sugar cannot be controlled by diet alone. Insulin is safe during pregnancy.
• Metformin or glyburide: Oral medications occasionally used as alternatives, though insulin remains the standard of care

After Delivery

GDM typically resolves after delivery, but follow-up is critical. A 75-gram OGTT should be performed 6–12 weeks postpartum to screen for persistent diabetes or pre-diabetes. Women with a history of GDM should be screened for type 2 diabetes every 1–3 years throughout their lives.