Gestational Diabetes

What is Gestational Diabetes?

Gestational diabetes mellitus (GDM) is a diagnosis made by your obstetrician or endocrinologist when your blood glucose levels are higher than normal during the pregnancy.  This occurs between 3 to 8% of pregnant women, and generally develops between the 24th and the 28th week of pregnancy.  Sometimes gestational diabetes may occur earlier in the pregnancy.

Gestational Diabetes Monitoring blood glucose levelsWhen a woman is pregnant, their body requires two to three times more insulin than when she is not pregnant. Gestational diabetes occurs when the body is not able to produce this increased insulin, leading to higher glucose levels than normal, as the action of insulin in the body is to reduce glucose levels.

Problems can arise in the pregnancy if gestational diabetes is not diagnosed and managed properly.  It can lead to problems with the baby’s growth (usually leading to big babies, but sometimes there can also be growth restriction, leading to small babies), and the risk of stillbirth is increased in mismanaged or undiagnosed gestational diabetes.

What are the Risk Factors for Gestational Diabetes?

The biggest risk factor for developing gestational diabetes is a past history of the condition in a previous pregnancy.

Other risk factors for Gestational diabetes include:

  • Age over 30
  • Family history of type 2 diabetes
  • Overweight or obesity
  • Polycystic Ovary Syndrome (PCOS)
  • Previously given birth to a large baby
  • Family history of gestational diabetes

Gestational diabetes is also more common in women of the following ethnicity:

  • Indigenous Australian or Torres Strait Islander background
  • Vietnamese, Chinese, Middle Eastern, Polynesian or Melanesian background

How is Gestational Diabetes best managed?

Gestational diabetes is best managed in a multi-disciplinary team, involving the obstetrician, diabetes educatordietitian, endocrinologist and the GP.  Dr Ken Law will lead this multi-disciplinary team to optimally manage your gestational diabetes.

Blood Glucose Level Monitoring

Monitoring the blood glucose levels during the pregnancy is vital to ensuring that optimal outcomes are achieved in the pregnancy.  This usually involves checking the blood glucose levels 4 times per day – before breakfast, and then 2 hours after the commencement of each meal.

The targets for blood glucose levels are:

  • Fasting (pre-prandial) <5.1 mmol/L
  • 2 hour after meals (post-prandial) < 6.8 mmol/L

These targets for blood glucose levels are much stricter than the targets that people with type 2 diabetes aim for.  This is because stricter glycaemic control has been shown to result in better outcomes for women and babies in gestational diabetes.

Healthy Diet and Physical Activity

Healthy exercise and adopting a healthy eating pattern are essential to optimising blood glucose levels.  If such lifestyle modifications are not enough to achieve good glycaemic control, then further medical intervention may be required.  This may involve the use of oral medications (e.g. Metformin), and some women may need to use insulin injections during the pregnancy to better control the glucose levels.

What Foods should you eat if you have Gestational Diabetes?


The body’s digestive system breaks down Carbohydrate foods into glucose, and this glucose is then used for energy. Carbohydrates are very important for you and your growing baby. However it is important to spread your carbohydrate foods over 3 small meals and 2 to 3 snacks per day, in order to  help manage the blood glucose levels.

The following foods are rich in carbohydrate:

  • breads and breakfast cereals
  • pasta, rice and noodles
  • starchy vegetables such as potato, sweet potato, corn, taro and cassava
  • legumes such as baked beans, red kidney beans and lentils
  • fruit
  • milk, yoghurt, dairy
  • desserts and calcium
  • fortified soy milk.

It is best to avoid carbohydrate foods that contain little nutritional value.  These include:

  • sugar (sucrose)
  • soft drinks
  • cordials, fruit juices
  • lollies
  • cakes and biscuits.

In some instances, women with gestational diabetes may already be eating the right amount and type of carbohydrate foods for their body, but still have high blood glucose levels. In this situation, it is important not to cut back on carbohydrates, and medications such as Metformin or insulin injections may be considered.


It is important to try to limit the amount of fat you eat, particularly saturated fat, and this is even more important in women with gestational diabetes. For cooking, use healthy fats such as canola, olive and polyunsaturated oils, and margarines, avocados and unsalted nuts.
The overall aim is to reduce your intake of saturated fat.  Choose lean meats, skinless chicken and low fat dairy foods. Avoid takeaway and processed foods.

While fat does not directly affect your blood glucose levels, all fats can cause extra weight gain, especially if eaten in large amounts.  This will ultimately make it more difficult to control blood glucose levels.


As protein is important for the growth and maintenance of the body, and the growing fetus, try to include 2 small serves of protein per day.   Foods rich in protein include:

  • lean meat,
  • skinless chicken,
  • fish,
  • eggs and reduced fat cheese.

These foods do not affect your blood glucose levels directly.

While milk, yoghurts, custards and legumes are important sources of protein, it is important to remember that they also contain carbohydrate.

Calcium and iron

During pregnancy, calcium and iron requirements are increased. It is recommended that pregnant women should include 3 serves of low fat, calcium-rich foods each day.

Examples of one serve of calcium-rich foods include:

  • 250ml low fat milk or calcium fortified soy milk,
  • 200g of yoghurt, or
  • 2 slices (40g) of reduced fat cheese

The iron from red meat, chicken and fish is well absorbed by the body.  However, vegetarians and women who do not eat these foods regularly may need iron supplementation or may need to take pregnancy multi-vitamins.

Healthy eating during pregnancy

Other dietary considerations

The overall aim in pregnancy is to eat nutritious foods that will not cause excess weight gain or cause the blood glucose levels to go up. These foods include:

  • low carbohydrate fruit such as strawberries, passionfruit, lemons and limes;
  • low carbohydrate vegetables such as salad, stir fry or green vegetables.

A healthy balanced diet should include at least 5 serves of vegetables per day.

In pregnancy, it is important to remember to continue to avoid those foods that are at risk for Listeria.

Women who have a family history of food allergies or intolerances should seek advice from their obstetrician or dietitian, as it may be advisable to avoid certain foods during pregnancy.

What are healthy drinks during pregnancy?

Choose mainly water, plain mineral water and soda water.  For some variety, try adding some fresh lemon or lime.  Soft drinks and other sweet drinks should be minimised.

Can artificial sweeteners be used during pregnancy?

All alternative sweeteners available in Australia have been thoroughly tested and approved by Food Standards Australia and New Zealand (FSANZ).  These are generally considered safe to eat.

What are the implications of having Gestational Diabetes?

After the birth of the baby, the woman’s glucose level generally improves.  However women who have had gestational diabetes are at an increased risk of developing type 2 diabetes, with up to 50% chance of developing diabetes within 20 years of a gestational diabetes pregnancy.  Therefore it is recommended that women who have had gestational diabetes have screening tests performed on a regular basis to look for type 2 diabetes in the long-term.

To discuss your personal situation and specific advice for you, , or his dietitian.

Greenslopes Obstetrics and Gynaecology