Gestational diabetes

Around 10-15% of pregnant people will get gestational diabetes (GDM) between the 24th and the 28th week of pregnancy, sometimes earlier. It usually goes away after the baby is born.

Some are more likely to get gestational diabetes. These include those who:

  • are from certain ethnic backgrounds, including our First Nations, South Asian, Vietnamese, Chinese, Middle Eastern, Hispanic, South American and Polynesian/Melanesian communities
  • have a close family history of type 2 diabetes such as a parent, brother or sister, or a sister with GDM
  • are over the age of 30 years, especially if you are over 40 
  • are above a healthy weight range 
  • have previously had a large baby, especially if the baby weighed more than 4.5 kg
  • have underlying medical conditions such as Polycystic Ovarian Syndrome (PCOS)
  • take certain medications such as antipsychotics or corticosteroids
  • have previously been diagnosed with GDM
  • have gained weight rapidly in the first half of their pregnancy.
What is gestational diabetes?

Diabetes is a condition where there is too much glucose (sugar) in the blood. The hormone insulin moves glucose from your blood and into your body's cells, where it is used for energy. When you have diabetes, this process is blocked, and your cells become 'insulin resistant'. This causes you to have too much glucose in your blood. In pregnancy, the hormones from the placenta, which help your baby grow, can cause your cells to become insulin resistant. Usually, in pregnancy, the body produces more insulin to counter this. In some pregnant people, however, this doesn't happen, and they develop gestational diabetes.

There are several health issues associated with gestational diabetes, including that both the birth parent and baby will have an increased risk of developing type 2 diabetes later in life. During the pregnancy, consistently high blood glucose levels can lead to excessive sugar and fats crossing the placenta, affecting the baby's growth, usually making them bigger. Giving birth to larger babies can also lead to problems with the delivery. Sometimes, even though it might not seem to make sense, some babies (particularly larger babies) are born with blood sugar levels that are too low - this is called hypoglycaemia. Gestational diabetes does not mean that your baby will be born with diabetes.

Well-managed gestational diabetes reduces the risk of these health problems for you and your baby. Your diabetes team (doctor, dietitian, diabetes educator) will help you to learn how to manage gestational diabetes so that your blood glucose levels stay within the target range.

Testing for gestational diabetes

If you are pregnant, you should be tested for gestational diabetes during your pregnancy. An Oral Glucose Tolerance Test (OGTT) is used to identify those who may have elevated blood sugars. The GTT assesses how your body responds to a 'glucose load' or how efficiently the glucose is moved from your blood to your body's cells. You must fast for 8 to 12 hours (you may drink water during this period), and then you have a blood test. After the blood test, you have a drink that contains glucose. One and two hours after you have the drink, the blood test is repeated. Gestational diabetes will be diagnosed if your blood sugar levels are above what they should be.

Managing gestational diabetes

Gestational diabetes can be managed with healthy eating, physical activity, monitoring your blood glucose levels and, sometimes, medication. At the Women's, a diabetes educator and dietitian will help you learn how to manage your gestational diabetes.


A nutritious diet can keep your blood glucose levels within target and nourish you and your baby. You are encouraged to eat three main meals and 2-3 mid-meals, spread throughout the day.

Your diet should be enjoyable and varied, low in saturated fat and high in fibre. Choose nutritious carbohydrate foods with a low glycaemic index (GI) such as multigrain breads, rice (such as low GI or basmati rice), and high fibre pasta. Legumes such as baked beans, red kidney beans and lentils, fruit, milk and yoghurt (either dairy or soy) are also good choices. Avoid carbohydrates that have little nutritional value like cakes, biscuits, juices and soft drinks.

See the section on healthy pregnancy for more information about diet and exercise.

Staying active

Physical activity helps improve insulin sensitivity, which helps manage blood glucose levels. Regular exercise helps to increase fitness levels and prepares you for labour.

Aim to do physical activity at an intensity that pushes you to work at a moderate pace, but not to the point of being out of breath.

To achieve and maintain a reasonable level of fitness aim for one of the following:

  • a session of moderate-intensity exercise on all or most days of the week
  • at least 150 minutes of exercise over a week
  • 10,000 steps per day.

Remember, before starting or continuing any form of physical activity, always check with your obstetrician or midwife.


If you have gestational diabetes, you will need to learn how to measure your blood glucose levels. You will be given a blood glucose monitor at the hospital. Your doctor or Diabetes Educator will advise you on recommended blood glucose targets and testing times. Daily blood glucose monitoring can help you understand the link between blood glucose, food, and exercise.

After your baby is born

If you are diagnosed with gestational diabetes, it is very important that you have regular follow-up tests for diabetes after the pregnancy or before becoming pregnant again. Go to your doctor when your baby is 6 -12 weeks old to get another oral glucose tolerance test (OGTT). This allows you to monitor and manage 'impaired glucose tolerance', or Type 2 diabetes.


The Women’s does not accept any liability to any person for the information or advice (or use of such information or advice) which is provided on the Website or incorporated into it by reference. The Women’s provide this information on the understanding that all persons accessing it take responsibility for assessing its relevance and accuracy. Women are encouraged to discuss their health needs with a health practitioner. If you have concerns about your health, you should seek advice from your health care provider or if you require urgent care you should go to the nearest Emergency Dept.