Gestational diabetes mellitus is a form of diabetes that occurs during pregnancy. Most women will no longer have diabetes after the baby is born. However, some women will continue to have high blood glucose levels after delivery. It is diagnosed when higher than normal blood glucose levels first appear during pregnancy.

Gestational diabetes is the fastest growing type of diabetes in Australia, affecting thousands of pregnant women. Between 12% and 14% of pregnant women will develop gestational diabetes and this usually occurs around the 24th to 28th week of pregnancy. All pregnant women should be tested for gestational diabetes at 24-28 weeks of pregnancy (except those women who already have diabetes). Women who have risk factors for gestational diabetes should be tested earlier in their pregnancy.

Who is at increased risk of gestational diabetes?

Women at increased risk of developing gestational diabetes include those who:

● Are aged 40 years or over
● Have a family history of type 2 diabetes or a first-degree relative (mother or sister) who has had gestational diabetes
● Are above the healthy weight range
● Have had elevated blood glucose levels in the past
● Are from Aboriginal and Torres Strait Islander backgrounds
● Are from a Melanesian, Polynesian, Chinese, Southeast Asian, Middle Eastern or Indian background
● Have had gestational diabetes during previous pregnancies
● Have previously had Polycystic Ovary Syndrome
● Have previously given birth to a large baby (weighing more than 4.5kg)
● Are taking some types of anti-psychotic or steroid medications
● Have gained weight too rapidly in the first half of pregnancy
● Gestational diabetes may also occur in women with no known risk factors.

How is gestational diabetes diagnosed?

Gestational diabetes is diagnosed using an oral glucose tolerance test (OGTT). This is done at a pathology lab. You will need to fast overnight before having this test. Blood will be taken to check your fasting blood glucose level. After this, you will be given a sugary drink and have your blood tested one and two hours later. You will be asked to sit and wait between tests. If your blood glucose level is above the normal range at your fasting, one or two hour test, you have gestational diabetes.