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What is gestational diabetes?

Gestational diabetes, often referred to as GDM, is a condition you may develop during pregnancy. It will be diagnosed with a blood test and an oral glucose tolerance test when you are between 24 and 28 weeks pregnant. It occurs when the hormones made by your placenta during pregnancy stop your body’s insulin from working properly, causing your blood glucose levels to rise.

If you’re diagnosed with gestational diabetes don’t panic. You haven’t done anything wrong and you are not alone.

Gestational diabetes affects between 10 and 14 per cent of Australian women during pregnancy. It can be managed with diet and exercise, although some women may require medication or insulin.

Gestational diabetes usually disappears after the birth, although it increases your risk of developing type 2 diabetes later in life.

Why does gestational diabetes happen?

There are two main reasons gestational diabetes may occur during your pregnancy. It’s a combination of insulin resistance and inability to produce enough insulin:

  • Your placenta produces a hormone called Human Placental Lactogen (HPL) that decreases the sensitivity of tissue cells to insulin, leading to high blood glucose levels
  • Your body can’t produce enough insulin to meet the extra needs of pregnancy.

If found during the first 12 weeks, it may mean that you had diabetes before, but it was only discovered because of your pregnancy.

What risk factors are associated with gestational diabetes?

Factors that may increase your risk of developing GDM during pregnancy include:

  • Being overweight or obese
  • A family history of type 2 diabetes
  • Certain ethnic backgrounds, including aboriginal or Torres Strait Islander, Indian, Vietnamese, Chinese, Middle Eastern or Polynesian
  • Having gestational diabetes during your previous pregnancies
  • Your age – you’re at greater risk if you’re over 30
  • Unexplained stillbirth or neonatal deaths or having previously given birth to a very large baby could all put you at greater risk of gestational diabetes

When will you be tested for gestational diabetes?

You’ll normally be tested for gestational diabetes in the 24th to 28th week of your pregnancy. It is diagnosed with an oral glucose tolerance test, which involves a fasting blood test, then again two hours after a glucose drink.

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