Gestational diabetes

 

Clinical features

  1. Gestational diabetes risk factors include:
  2. Glycosuria
  3. Age over 30 years
  4. Obesity
  5. Family history of diabetes
  6. Past history of gestational diabetes or glucose intolerance
  7. Previous adverse pregnancy outcome
  8. Belonging to an ethnic group with a high risk for gestational diabetes
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Genetics

  1. Patients with MODY due to a mutation in the glucokinase gene (GCK, described above) have mild fasting
    hyperglycaemia throughout life and may present during pregnancy when routine testing is performed.
  2. Since these patients have a consistently raised fasting blood glucose they will have macrosomic children
    (as long as their child does not have the mutation).
  3. The diagnosis of a GCK mutation is important because:
  4. The child may subsequently be picked up as having a raised fasting blood glucose associated with
    type 1 diabetes
  5. Different guidelines will be given to the mother
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Prevalence

  1. Ethnicity is a particularly important factor determining the incidence of gestational diabetes.
  2. Very high risk: Australian Indigenous, Polynesian and South Asian/Indian groups
  3. Moderate to high risk: Middle Eastern and other Asian groups.
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Investigations

  1. The following criteria identify when GCK testing may be considered:
  2. Persistently raised fasting blood glucose in the range of 5.5 – 8 mmol/L before, during and after
    pregnancy
  3. An increment of <4.6 mmol/L on at least one oral glucose tolerance test (either during or after pregnancy)
  4. A parent may have mild type 2 diabetes but often this has not been detected and so the absence of family history should not exclude the diagnosis
  5. Genetic testing may be available in Australia with out-of-pocket expenses.
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