Gestational Diabetes

Pregnancy is an exciting and turbulent time, full of new experiences both good and bad. During pregnancy you do everything you can to look after your own health, knowing your baby’s future health depends on it.

Gestational diabetes is a disease occurring only during pregnancy. It can threaten the well being of both you and your baby, while you are pregnant and also after your baby is born. Unfortunately, gestational diabetes rarely exhibits any symptoms, so it’s crucial you’re aware of the risk factors for this condition, and are screened for the disease.

What is gestational diabetes?

Gestational diabetes is a temporary form of diabetes which begins during pregnancy and usually disappears after delivery of your baby. It affects between 3 to 8% of pregnant Australian women.

As with diabetes, gestational diabetes means your body is unable to make and use enough insulin. In gestational diabetes, insulin is blocked from doing its job – this is called insulin resistance. Without enough insulin, glucose can’t move from your blood to your body’s cells where it’s converted to energy. Instead, it remains in your blood where it accumulates. This is called hyperglycaemia.

Insulin resistance in women with gestational diabetes is actually caused by hormones in the placenta interfering with insulin. The function of the placenta in pregnancy is to supply your growing baby with nutrients and water from the mother’s circulation. In this process, the placenta produces a number of hormones which play a critical role in maintaining the pregnancy. Unfortunately, some hormones produced in the placenta, such as oestrogen, cortisol, and human placental lactogen (HPL), can block insulin. This usually begins in weeks 24-28 of pregnancy, and worsens as the pregnancy develops and the placenta becomes larger.

Any woman can develop gestational diabetes during pregnancy, though there are a number of high risk factors. These include:

  • Obesity
  • A family history of Type 2 diabetes
  • Previous difficulties carrying a pregnancy to term
  • Being older than 30 years of age
  • Being of Indigenous Australian or Torres Strait Islander nationality
  • Having gestational diabetes during previous pregnancies
  • Being of certain ethnic ancestry, including Indian, Chinese, Polynesian/Melanesian, Vietnamese or Middle Eastern

Testing for gestational diabetes

Testing for gestational diabetes is usually carried out between 24 to 28 weeks into the pregnancy, although those with high risk factors may be tested earlier.

The most common screening test for gestational diabetes is the Glucose Challenge Test (GCT), where blood is taken for a glucose measurement one hour after drinking a glucose solution. If test results are abnormal, an Oral Glucose Tolerance Test (OGTT) is done. For an OGTT a blood sample is taken both before and two hours after consuming another glucose drink.

Current research: Research published in the February 2004 issue of Diabetes Care suggests measuring the size of the unborn baby may provide a more accurate indication of gestational diabetes than testing the mother’s blood glucose levels. Using ultrasound technology, researchers found giving insulin only to mothers whose baby’s abdominal size was in the 75th percentile or higher produced better results than giving it to all mothers whose blood glucose levels were higher than normal.

Is gestational diabetes harmful?

If gestational diabetes is managed well and blood sugars are kept under control, no harm should come to you or your baby. Because gestational diabetes usually occurs in late pregnancy, the baby’s development is not normally affected. However, untreated or poorly controlled gestational diabetes can cause the following complications:

Macrosomia. Gestational diabetes can result in a larger than normal baby. The baby receives all of its food and nutrients from the mother’s blood. If the mother’s blood contains too much glucose, the baby’s pancreas will sense this and produce extra insulin in an attempt to get rid of any extra glucose. Because the baby is getting more energy than it needs, the extra energy is stored as fat.

Delivery problems. Babies with macrosomia can incur damage to their bones and nerves in their arms and shoulders during delivery. Sometimes a caesarian section may be necessary to deliver the baby if it’s too large.

Low blood sugar levels. Gestational diabetes can increase the newborn’s risk of developing low blood glucose levels. After birth, the baby continues to produce a high level of insulin, but is no longer receiving excess glucose from its mother, thereby causing blood sugar levels to drop. The baby’s blood sugar levels should be checked shortly after birth and rectified intravenously if necessary.

Obesity and Type 2 diabetes. Babies with excess insulin are at greater risk of obesity as children, and have an increased risk of developing Type 2 diabetes as adults, both of which lead to other health complications.

Jaundice. Untreated gestational diabetes can also result in jaundice for the newborn. Jaundice is a build up of old red blood cells which the body can’t process fast enough. This problem is rectified with treatment.

Treating and managing gestational diabetes

The most important goal in treating gestational diabetes is to control your blood glucose levels. This can usually be achieved effectively through:

  • Special meal plans
  • Regular exercise
  • Regular blood glucose testing

A doctor or dietitian can recommend a specialised meal plan taking into account your weight, stage of pregnancy, food preferences, level of exercise, and any other relevant factors. Also, ask your doctor to help you design a balanced exercise program. The more regularly you exercise, the better your blood glucose control should be. Be careful when you exercise though; make sure your pulse doesn’t get too elevated and the exercise isn’t too strenuous. If you experience any unusual pain during exercise, call your doctor immediately.

You can use a food and exercise diary to log your food and activities. Try Allan Borushek’s Pocket Food and Exercise Diary or an electronic diary, such as our Food and Exercise Diary. If exercise and diet are not effective in stabilising your blood glucose levels, you may require insulin injections. Your doctor will advise you on this.

Blood glucose testing is important to help you monitor how well you’re controlling your insulin levels. Testing can be done by your doctor or at home. Your doctor or diabetes educator may provide you with a user-friendly blood glucose monitoring machine and teach you how to read your blood glucose and food intake profiles.

Post-natal concerns

Gestational diabetes usually disappears after pregnancy. However, if you’ve had gestational diabetes, you face an increased risk of developing Type 2 diabetes later in life, with a 30 to 50% chance of developing type 2 within 15 years of your pregnancy. You also have an increased chance of gestational diabetes occurring in any future pregnancies. These risks are further increased if you’re overweight. To help lower your risk of future diabetes, take these steps to maintain a healthy lifestyle:

  • Maintain a healthy weight and aim to minimise extra fat – especially around your waist.
  • Make wise food choices.
  • Exercise regularly and with variety.
  • Before considering another pregnancy, get your doctor or diabetes educator to monitor your blood sugar levels.


This article was compiled in consultation with health experts and in reference to the following sources:

Diabetes Australia, ‘Gestational Diabetes’,

National Institute of Child Health and Human Development, ‘Are You at Risk for Gestational Diabetes?’

Tori Kordella, ‘Gestational Diabetes: Are Prediction and Prevention Possible?’ Diabetes Forecast, January 2004

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