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What is gestational diabetes?
Gestational diabetes mellitus (GDM) is diabetes first recognized in pregnancy. This can occur in up to 20% of pregnant women and can often go undetected. If left untreated though, it can lead to complications for you and your baby.
What causes gestational diabetes?
When you’re pregnant, gestational diabetes can occur if your body can’t produce enough insulin to adapt to the effects of a growing baby and your changing hormone levels. The cells become resistant to the action of insulin, and in turn, the pancreas cannot secrete enough insulin to counterbalance the effect of these hormones. This initially causes hyperglycemia (high blood sugar levels) and then eventually diabetes.

What are the symptoms of gestational diabetes?
Unfortunately, you may not even realize you have gestational diabetes because there are not always obvious symptoms. Some people may experience extreme tiredness, excessive thirst, headaches and an increase in the amount and frequency of urination. Your care team may notice that the baby’s measurements are ahead of schedule and is “large for dates.” This is due to the excess glucose from you and the ability to store this by your baby.
How is gestational diabetes diagnosed?
Canadian clinical guidelines for diabetes recommend that all pregnant women get tested for GDM between the 24th and 28th week of their pregnancy. If a woman has risk factors, then this may be done earlier or repeated at any time that there is concern for GDM.
There are two approaches for diagnosis. The first is a preferred test, which is a 50-gram drink of a glucose solution taken in a non-fasting state (can be done at any time of day) followed by a blood sugar test one hour later. If this is abnormal, then a second test is done. This second test which consists of 75grams of glucose is done in a fasting state and is followed by a fasting blood test and at 1 and 2 hours. Alternatively, this fasting test can be done at the outset instead of the 50-gram test. However, most women and doctors prefer the easier non-fasting 50-gram test.
Generally, an A1C is not used for diagnosis as it takes 2-3 months to show an increase in glucose, but if there is concern that a person has undiagnosed type 2 diabetes prior to pregnancy, this may be done in the first trimester. If elevated, this is diagnostic of pre-existing type 2 diabetes that has not been caught prior to pregnancy.

Are some women at greater risk of developing GDM?
There are several factors that can increase your risk of developing gestational diabetes such as:
- Having family members with type 2 diabetes
- Living with obesity or overweight
- Being over the age of 35
- Having previously given birth to a larger baby (more than 9 lbs/4000grams)
- Certain ethnicities (Aboriginal, Latin American, Asian and African)
- Having regularly used a corticosteroid medication
- If you had gestational diabetes in the past
- If you have polycystic ovary syndrome
What are the risks of gestational diabetes?
Fortunately, you can manage gestational diabetes to decrease your chances of complications during pregnancy. But when left untreated, the condition can increase your risk for a bigger baby (greater than 9 lbs) and a harder, more complicated delivery, sometimes requiring Caesarean section.
Women with gestational diabetes also have an increased risk for high blood pressure and swelling, as well as excess amniotic fluid, and premature birth.
Gestational diabetes can also increase the chances of you and your baby developing type 2 diabetes in the future. It can increase the risk of your child becoming obese in early adulthood as well.

How is gestational diabetes managed?
It is important for gestational diabetes to be managed during pregnancy and after delivery. Proper management of gestational diabetes includes following a healthy low glycemic meal plan, staying physically active, monitoring your blood sugars, and taking your medications as prescribed.
Articles about Gestational Diabetes
- Diabetes for two...diabetes diagnosis during pregnancyThere are several types of 'diabetes in pregnancy'. Diabetes can sometimes present for the first time during a pregnancy. This type, which is usually picked up by a routine test about half way through the pregnancy, is called gestational diabetes.
- What are the risks of having gestational diabetes?Gestational diabetes is a temporary form of diabetes that occurs during pregnancy. It is estimated that 3% to 20% of women across Canada will develop gestational diabetes every year. So what are the risks of having gestational diabetes?
- Managing a diagnosis of gestational diabetesPregnancy can present challenges for any women. However, managing a diagnosis of gestational diabetes can add additional challenges and therefore result in new stressors in a woman’s life.
- Life after gestational diabetesGestational diabetes (GDM) is a temporary form of diabetes that can arise during pregnancy.