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GDM — Screening & Diagnosis Notes

When to Screen

If test is normal at first visit → repeat at 24–28 weeks → if still normal → retest at 32–34 weeks.

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Screening Methods

Single-Step Methods

• Convenient, economical, does NOT require fasting

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1. DIPSI Method (Diabetes in Pregnancy Study Group India)

• Give 75 g glucose in 300 mL water
• Irrespective of last meal / fasting state
• Glucose water consumed slowly over ~5 minutes (to avoid nausea/vomiting)
• Lemon juice can be added for palatability
• Venous blood drawn 2 hours after glucose consumption
• Tested by autoanalyser / semi-autoanalyser; or glucometer calibrated to plasma glucose

If patient vomits within 30 minutes → repeat OGCT or check FBS + PPBS

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2. IADPSG Criteria

• Woman comes after overnight fasting → fasting plasma glucose checked
• Given 75 g glucose in 150 mL water or lime juice
• Plasma glucose checked at 1 hour and 2 hours

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3. WHO Method

• Universal screening at 24–28 weeks
• 75 g 2-hour GTT (fasting state)
• 2-hour plasma glucose ≥ 140 mg/dL → diagnostic of GDM

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Two-Step Method (used in some countries)

• Given irrespective of last meal
• Done at 24–28 weeks (in women without pre-existing diabetes)
• If 1-hour plasma glucose ≥ 140 mg/dL → proceed to Step 2

• Plasma glucose checked at fasting, 1, 2, and 3 hours
• GDM diagnosed if ANY TWO values are abnormal:

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Quick Comparison Summary

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Diabetes in Pregnancy — Part 3

Complications & Lung Maturity Tests

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A. MATERNAL COMPLICATIONS

1. Hyperglycemia

2. Infections — increased risk of:

• Asymptomatic bacteruria
• Candidiasis
• Puerperal sepsis

3. Polyhydramnios → More amniotic fluid

• Measured by USG
• Normal Amniotic Fluid Index (AFI): 5–25
• Polyhydramnios: AFI > 25 | Oligohydramnios: AFI < 5
• Due to microvascular stretching → pre-term labour
• Leads to: PTL (Pre-term Labour), PROM (Premature Rupture of Membranes), Cord prolapse, PPH, Subinvolution (uterus does not return to normal size)

4. Oligohydramnios

• Occurs if diabetic vasculopathy / PIH present

5. Big Placenta (Placentomegaly)

• Swelling of chorionic villi due to hyperglycemia
• Increases risk of: PIH, Placenta previa (placenta covering the opening of the uterine cervix)

6. Increased risk of:

• T2DM in the future
• Caesarean section
• Ketoacidosis

Notes:

• Pregestational diabetes with retinopathy → retinopathy worsens during pregnancy
• In all females with pre-GDM → conduct baseline fundus examination

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Hypoglycemia (Maternal)

• Blood sugar < 70 mg/dL
• Symptoms: Tremors, sweating, palpitations, extreme fatigue, tingling sensation
• Management:
  • 3 teaspoons glucose in 100 mL water, OR
  • 6 teaspoons sugar in 100 mL water

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B. FETAL COMPLICATIONS (Pederson's Hypothesis)

Maternal hyperglycemia
       ↓
Fetal hyperglycemia  →  Cardiac abnormalities
       ↓                Sacral dysgenesis
Stimulates fetal pancreas
       ↓
Hyperinsulinemia
  ↓ (insulin = growth hormone)     ↓ Lipolysis
↑ Growth                     ↑ Fat deposition (esp. around fetal shoulder)
       ↓
   MACROSOMIA
       ↓
Shoulder dystocia (difficulty in delivery of shoulder)

Note: Hormones needed for fetal growth = Insulin, IGFs

Consequences of Macrosomia:

• Prolonged labour
• Increased chances of Caesarean section

Other Fetal Complications:

• IUGR — only if diabetic vasculopathy / PIH present
• Increased risk of abortion — in uncontrolled diabetes
• Increased risk of stillbirth due to:
  • Macrosomia → ↑ oxygen demand → Hypoxia → Fetal death/stillbirth
  • Hyperglycemia → Oxidative stress → Edema of chorionic villi → ↓ oxygen transport → Hypoxia
  • Most common in last 4 weeks of pregnancy
• Congenital malformations — only in fetus of pre-GDM (not GDM)

Fetal Effects Summary:

• Spontaneous miscarriage
• Anomalies
• FGR (Fetal Growth Restriction)
• Macrosomia
• Prematurity
• IUD (Intrauterine Death)

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C. NEONATAL COMPLICATIONS

Note: Anemia is NOT seen as a complication.

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D. LATE COMPLICATIONS IN CHILD

• T2DM: 1–8%
• Obesity
• Metabolic X syndrome

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E. LUNG MATURITY TESTS

1. Lecithin/Sphingomyelin (L/S) Ratio — Most common test

2. Phosphatidyl Glycerol — Best test (done ≥ 35 weeks)

3. Lamellar Body Count

• Type 2 pneumocytes produce surfactant, released as packets = lamellar bodies

4. Bedside / Shake / Bubble Test — Obsolete

5. Nile Blue Sulphate Test — Obsolete

• Principle: AF has fetal skin cells → mature at same time as lungs
• Procedure: Take AF in test tube → add Nile blue sulphate dye → prepare slide → examine under microscope
  • Blue cells = Immature skin cells
  • Orange cells = Mature skin cells
• Interpretation: > 50% orange cells → Lungs mature