Diabetes Mellitus & Pregnancy: Gestational & Overt

For further information, see CMDT Part 19-20 Diabetes Mellitus in Pregnancy

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

  • HbA_1c determination

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

  • Funduscopic examination

  • ECG