Gestational Diabetes

Antenatal Obstetrics 

The following article regarding gestational diabetes is for informational purposes only and cannot be considered as professional advice. If you have any concerns or questions regarding gestational diabetes, please consult your obstetrician.

Gestational diabetes mellitus (GDM) is a condition that develops during pregnancy when the body is not able to make enough insulin.  The lack of insulin causes the blood glucose (also called blood sugar) level to become higher than normal. Gestational diabetes affects between 3 and 5 percent of women during pregnancy.

It is important to recognise and treat gestational diabetes as soon as possible to minimise the risk of complications in the baby.  In addition, it is important for women with a history of gestational diabetes to be tested for diabetes after pregnancy because of an increased risk of developing type 2 diabetes in the years following delivery.

Complications of gestational diabetes can include:

  • Having a large baby (weighing more than 9 lbs or 4.1 kg)
  • Injury to the mother or infant during delivery
  • Preeclampsia
  • An increased chance of needing a caesarean delivery

Screening for gestational diabetes is usually done between 24 and 28 weeks of pregnancy. However, screening may be done earlier in the pregnancy if you have risk factors for gestational diabetes, such as:

  • A history of gestational diabetes in a previous pregnancy
  • Obesity
  • Glucose (sugar) in your urine
  • A strong family history of diabetes

Gestational diabetes is diagnosed if you have two or more blood sugar values above the following levels:

  • Fasting: greater than 5.5 mmol/L and/or
  • Two-hour: greater than 7.9 mmol/L

If you are diagnosed with gestational diabetes, you will need to make changes in what you eat, and you will need to learn to check your blood sugar level.  In some cases, you will also need to learn how to give yourself insulin injections.
The goal of treatment for gestational diabetes is to reduce the risk that the baby will be large (weight greater than 9 lbs at birth).  A large baby can be hard to deliver through the pelvis.  This increases the risk of injuring the infant (eg, broken bones or nerve injury). A large baby is also more likely to cause injury to the woman during the delivery.

Changes in diet that are recommended include:

  • Avoiding high-calorie snacks and desserts, including soft drinks with sugar, fruit drinks, lollies, chips, biscuits, cakes, and full-fat ice cream
  • Using artificial sweeteners.  They have not been linked to an increased risk of birth defects.
  • Eating a lot of vegetables and fruits, at least five servings a day.
  • Choosing foods with whole grains.  This includes wholemeal bread, brown rice, or wholemeal pasta instead of white bread, white rice, or regular pasta.
  • Eating a limited amount of red meat, and choosing lean cuts of meat that end in “loin” (eg, pork loin, tenderloin, sirloin).
  • Choosing low- or fat-free dairy products, such as skim milk, non-fat yogurt, and low-fat cheese
  • Using liquid oils (olive, canola) instead of solid fats (butter, margarine, shortening) for cooking

Blood sugar monitoring and referral to an endocrinologist is recommended for women with gestational diabetes.


The management of labour or induction of labour will depend on the control of gestational diabetes and the need for insulin. Having gestational diabetes does increase your risk of developing type 2 diabetes later in life.
Women with gestational diabetes should have testing for type 2 diabetes at six weeks postpartum.  One-third to two-thirds of women who have gestational diabetes in one pregnancy will have it again in a later pregnancy.
The risk of developing type 2 diabetes is greatly affected by body weight.  Women who are obese have a 50 to 75 percent risk of type 2 diabetes, while women who are a normal weight have a less-than-25 percent risk.  If you are overweight or obese, you can reduce your risk of type 2 diabetes by losing weight and exercising regularly.

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