Skip to Main Content

Diabetes Mellitus & Pregnancy: Gestational & Overt

For further information, see CMDT Part 19-19: 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

    • 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.
View Table||Download (.pdf)
Table 19–4. Screening and diagnostic criteria for gestational diabetes mellitus.

Screening for gestational diabetes mellitus

  1. 50-g oral glucose load, administered between 24 and 28 weeks, without regard to time of day or time of last meal.

  2. Venous plasma glucose measured 1 hour later.

  3. Value of 140 mg/dL (7.8 mmol/L) or above in venous plasma indicates the need for a diagnostic glucose tolerance test.

Diagnosis of gestational diabetes mellitus

  1. 100-g oral glucose load, administered in the morning after overnight fast lasting at least 8 hours but not more than 14 hours, and following at least 3 days of unrestricted diet (> 150 g carbohydrate) and physical activity.

  2. Venous plasma glucose is measured fasting and at 1, 2, and 3 hours. Patient should remain seated and should not smoke throughout the test.

  3. The diagnosis of gestational diabetes is made when two or more of the following venous plasma concentrations are met or exceeded: fasting, 95 mg/dL (5.3 ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.

This site uses cookies to provide, maintain and improve your experience. MH Privacy Center Close