Diabetes screening in pregnancy

Gestational Diabetes - Sweet Trouble Ahead

• Universal screening at 24-28 weeks gestation; screen earlier if high-risk (obesity, prior GDM).
• Initial test is a 1-hr 50g glucose challenge test (GCT).
• Confirmatory test is a 3-hr 100g oral glucose tolerance test (OGTT).

• OGTT Abnormal Thresholds:
  • Fasting: ≥ 95 mg/dL
  • 1 hr: ≥ 180 mg/dL
  • 2 hr: ≥ 155 mg/dL
  • 3 hr: ≥ 140 mg/dL

⭐ Maternal GDM significantly increases fetal risk for macrosomia, neonatal hypoglycemia, and respiratory distress syndrome.

The Glucose Gauntlet - Screening Algorithm

Universal screening for all pregnant individuals occurs at 24-28 weeks gestation. The most common approach is the two-step method outlined below.

• 3-hr OGTT (100g) Diagnostic Criteria (Need ≥2 values):
  • Fasting: ≥ 95 mg/dL
  • 1-hour: ≥ 180 mg/dL
  • 2-hour: ≥ 155 mg/dL
  • 3-hour: ≥ 140 mg/dL

⭐ Screen high-risk patients (e.g., previous GDM, BMI >30, PCOS) in the first trimester. If negative, repeat screening at the standard 24-28 weeks.

Complications - Sugar's Ripple Effect

• Maternal Risks:

  • Preeclampsia / Eclampsia
  • ↑ Cesarean delivery rates
  • ↑ Future risk of Type 2 Diabetes & metabolic syndrome

• Fetal & Neonatal Cascade:

  • Maternal hyperglycemia → Fetal hyperglycemia → Fetal hyperinsulinemia (anabolic state).
  • Macrosomia: Birth weight >4-4.5 kg; can lead to birth trauma (e.g., shoulder dystocia, brachial plexus injury).
  • Hypoglycemia: Persistent hyperinsulinemia after placental separation.
  • Polycythemia & Hyperbilirubinemia: Fetal hypoxia from ↑metabolic demand → ↑EPO.
  • Hypocalcemia: Due to delayed parathyroid hormone production.

⭐ Fetal hyperinsulinemia antagonizes cortisol, preventing sphingomyelin maturation. This leads to a ↓ lecithin/sphingomyelin (L/S) ratio, causing Neonatal Respiratory Distress Syndrome (NRDS).

High‑Yield Points - ⚡ Biggest Takeaways

• Universal screening for Gestational Diabetes (GDM) is performed at 24-28 weeks gestation.
• The initial test is a 1-hour, 50-g glucose challenge; a value ≥140 mg/dL is considered positive.
• A positive screen requires a diagnostic 3-hour, 100-g oral glucose tolerance test (OGTT).
• GDM is diagnosed if two or more values on the 3-hour OGTT are elevated.
• Screen high-risk patients (e.g., prior GDM, obesity) at the first prenatal visit.
• The primary goal of GDM management is to prevent fetal macrosomia and related complications.