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Key Features

Essentials of Diagnosis

  • Gestational diabetes

    • Abnormal glucose tolerance in pregnancy

    • Believed to be an exaggeration of the pregnancy-induced physiologic changes in carbohydrate metabolism

  • Overt diabetes

    • Diabetes mellitus that antedates the pregnancy

    • Diagnosed in 50% of women with gestational diabetes at some point in their lifetime

General Considerations

  • Normal pregnancy can be characterized as a state of increased insulin resistance that helps ensure a steady stream of glucose delivery to the developing fetus

  • Thus, both mild fasting hypoglycemia and postprandial hyperglycemia are physiologic

  • These metabolic changes are believed to be hormonally mediated with likely contributions from human placental lactogen, estrogen, and progesterone

  • Women with diabetes should undergo preconception counseling and evaluation to maximize pregnancy outcomes

  • All pregnant women should undergo screening for gestational diabetes mellitus, either by history, clinical risk factors, or (most commonly) laboratory screening tests

Clinical Findings

Symptoms and Signs

  • Excessive fetal growth

  • Shoulder dystocia

  • Preeclampsia

  • Macrosomia

  • Hypertension is common in overt diabetes

  • Signs and symptoms of infections should be evaluated and promptly treated

Differential Diagnosis

  • Drugs: corticosteroids, thiazides, tacrolimus

  • Diabetes insipidus

  • Psychogenic polydipsia

  • Nondiabetic glycosuria (benign)

Diagnosis

Laboratory Tests

  • Euglycemia is considered to be 60–90 mg/dL (3.3–5.0 mmol/L) while fasting and < 120 mg/dL (< 6.7 mmol/L) 2 hours postprandially

  • A screening 50-g glucose load is administered at 24-28 weeks gestation

  • If this test is abnormal, the diagnostic test is a 100-g oral glucose tolerance test (Table 19–4)

  • Initial tests include

    • Complete chemistry panel

    • HbA1c determination

    • 24-hour urine collection for total protein and creatinine clearance

    • Funduscopic examination

    • ECG

Table 19–4.Screening and diagnostic criteria for gestational diabetes mellitus.

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