Gestational diabetes

Gestational diabetes mellitus (GDM) occurs during pregnancy. It is more commonly diagnosed in the second or third trimester. It affects between 10 and 20 per cent of Australian women during pregnancy.

Gestational diabetes occurs when the hormones made by the placenta during pregnancy stop the body’s insulin from working properly, causing blood glucose levels to rise. In most cases the condition disappears after the birth of the child, but it may put the mother at greater risk of another GDM diagnosis during future pregnancies, and women who have had gestational diabetes are more likely to develop type 2 diabetes after the birth/s.

Why does it happen?

There are two reasons GDM may occur in a pregnant woman:

  • because the body cannot produce enough insulin to meet the extra needs of pregnancy.
  • when found during the first trimester (first 12 weeks), it most likely existed beforehand, but was only discovered during pregnancy.
There were 32,000 women with GDM in Australia last year

GDM occurs in 10%-20% of pregnancies
and in most cases disappears after birth

What risk factors are associated with GDM?

Factors that may impact a woman’s GDM diagnoses during pregnancy include:

  • Obesity and being overweight
  • A family history of type 2 diabetes (including parent or sibling)
  • Cultural backgrounds can influence your risk including Aboriginal or Torres Strait Islanders, Indian, Vietnamese, Chinese, Middle Eastern or Polynesian
  • Gestational diabetes occurred during previous pregnancies
  • Your age – you are at greater risk of GDM if you are 30 years old or older
  • Unexplained stillbirth or neonatal deaths or having a very large infant previously could  put the mother at greater risk

When will I be tested for GDM?

A test called an oral glucose tolerance test (OGTT) is used to diagnose GDM and involves a blood test before breakfast, then again two hours after a glucose drink.

This test generally occurs in the 24th – 28th week of pregnancy.


What happens next?

Usually gestational diabetes goes away after your baby is born and you should be able to cease taking any associated medication (tablets or insulin). Before you are discharged to the care of your GP, your blood will be tested to make sure the glucose levels have returned to normal. You should have a fasting blood test six weeks after your baby is born and then every year.


I was diagnosed with GDM – what do I do?

Looking after gestational diabetes is important to prevent complications during pregnancy and childbirth. Management for GDM includes:

  • A dietitian who will help you with a healthy eating plan that meets the nutritional requirements of pregnancy and is appropriate for your blood glucose levels
  • An exercise physiologist or local doctor will recommend regular physical activity to help your body’s insulin work better. It also helps manage blood glucose levels
  • Frequent blood glucose monitoring will help manage blood glucose levels to stay in the target range for a healthy pregnancy

Some women may also require insulin injections to help manage blood glucose levels.

If your blood glucose cannot be controlled by diet, you may need to take tablets or insulin injections to treat your diabetes.

Who else can help me?

If you are diagnosed with GDM you will be able to manage your condition with specialist help from your doctor, diabetes educator and dietitian.

You are more likely to develop GDM again if you have had it in previous pregnancies, and women with GDM have an increased risk of developing Type 2 diabetes during their lifetime.

If you need more information or support, call Diabetes NSW on 1300 342 238.

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