Gestational diabetes - What is it?

What is gestational diabetes?

Gestational diabetes mellitus (GDM) is a temporary condition that occurs during pregnancy. Women who develop this complication do not have diabetes prior to becoming pregnant. It can affect about 3-12 per cent of pregnant women.

When should pregnant women be screened for gestational diabetes?

All women should be screened for gestational diabetes to reduce the incidence of having a large birth weight baby. Screening should take place between 24 to 28 weeks of pregnancy, or earlier if there are risk factors. 

How will I be screened for gestational diabetes?

Screening may involve taking your medical history and examining risk factors, but an oral glucose (sugar) tolerance test is also recommended.

What is the oral glucose tolerance test?

The oral glucose tolerance test is called the “Trutol Screening” test. This test will measure your body’s ability to use glucose. The test involves drinking a sweetened liquid which contains 50 gram of glucose. The body absorbs this glucose rapidly, causing blood glucose levels to rise within 30-60 minutes. A blood sample will be taken about one hour after drinking the solution. The blood test will measure how the glucose solution was processed by the body.

If the blood glucose level is:

  • between 7.8-11.0 mmol/L further testing will be needed, or
  • 11.1  mmol/L or above indicates gestational diabetes.

What if I am diagnosed with gestational diabetes?

If you have been diagnosed with gestational diabetes, you are at greater risk of having:

  • high blood pressure (preeclampsia);
  • infections, especially vaginal, bladder, and kidney;
  • a cesarean section; and
  • birth complications (e.g. longer labour).

What can I do to manage my gestational diabetes?

You will need to keep track of your glucose levels (usually before breakfast and 1 hour after meals). The target range for your blood glucose levels should be:
Before meals and bedtime snack:  less than 5.3 mmol/L
One hour after meals:  less than 7.8 mmol/L

To manage your gestational diabetes you should also:

  • follow a meal plan and have a healthy diet;
  • be physically active;
  • test your urine for ketones; and/or
  • use insulin, if your meal plan and regular activity cannot control your blood glucose level.

Will my baby be born with diabetes?

No, having gestational diabetes will not cause your baby to be born with diabetes. Your baby has a greater risk of developing diabetes as an adult, and female children may be more likely to develop gestational diabetes during their own pregnancies.

How can gestational diabetes affect my baby?

Your baby may:

  • have a large birth weight (over 9lbs or 4kg);
  • have low blood glucose at birth;
  • be jaundice (yellowing of the skin);
  • have respiratory problems, such as respiratory distress syndrome; and/or
  • have an increased risk for developing diabetes, obesity and heart disease as an adult.

What if I have a large birth weight baby?

Large birth weight babies (over 9lbs or 4kg) may have an increased risk for getting diabetes as an adult.

What are the risk factors for gestational diabetes?

Some of the risk factors for gestational diabetes include:

  • being overweight;
  • having a family history of diabetes;
  • having gestational diabetes during a previous pregnancy;
  • having a previous stillbirth;
  • having delivered a baby that weighed over 9 pounds; and
  • being over 25 years of age.

Will my gestational diabetes go away after my baby is born?

Most women who develop diabetes during pregnancy go on to have healthy babies and the diabetes usually disappears following the delivery of the baby. However, research has shown that within 5-15 years of having gestational diabetes during pregnancy, 50% of those mothers developed type 2 diabetes.

After having your baby, it is important to continue to adopt a healthy, active lifestyle to delay or prevent the onset of diabetes. It is also important to speak to your family physician / nurse practitioner about getting screened for type 2 diabetes. 

For more information, visit Diabetes Canada 


Published date: 
June 30, 2021
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