Gestational Diabetes

Diabetes is a disorder where the patient is unable to regulate sugar levels in their blood. The hormonal changes associated with pregnancy makes your body less efficient at using sugar. For most women, this will not be a problem, but about 3-6% of women in Canada will develop gestational diabetes. 

How would I know if I have gestational diabetes?

urine test

Unlike diabetes that occurs outside of pregnancy, most pregnant women with gestation diabetes have no symptoms of diabetes like weight loss or excessive thirst. Most women will be asked to do a glucose challenge test (GCT) between 24-28 weeks. This is not a fasting test. You eat a normal breakfast and then go to the lab in the morning. They will give you a drink. You wait for one hour and then a blood test is done. If the results are normal, you do not have diabetes.

If the results are high, you will be asked to repeat the test, but this time after fasting for eight (8) hours (usually overnight). This second test is called a glucose tolerance test (GTT) and involves having your blood taken before you have the drink, one hour after the drink and again two hours after the drink. If any of these results are not normal, you will be referred to the Diabetes Education Centre where you will be educated about the right diet for you and how to monitor your blood sugar.

Learn more on the Diabetes Canada website. 
Find out more about gestational diabetes on the website.

Glucose Challenge Test (GCT)

  • Done between 24-28 weeks
  • Eat a normal breakfast
  • Go to lab before 11a.m.
  • Have a special orange drink
  • Wait one hour, then do blood test
  • If this is normal, no gestational diabetes
  • If this is not normal, do GTT

Glucose Tolerance Test (GTT)

  • Done if GCT abnormal
  • Fast for 8 hours
  • Do three sets of blood tests
    • one before the drink
    • one an hour after the drink
    • one two hours after the drink
  • If this is normal, you don’t have diabetes, even if the GCT was abnormal
  • If this is abnormal, you have diabetes and will be referred to  north York General Hospital’s Diabetes Education Centre

Women who develop gestational diabetes are 10-50% more likely to develop diabetes later in life when they are not pregnant. Exercise, weight control and a healthy diet now can help reduce your future risk.

 Who is at risk for gestational diabetes?

  • Previous history of gestational diabetes
  • Women pregnant with twins
  • A family history of diabetes
  • Previous large baby (> 4kg) or suspected large baby now
  • Previous unexplained stillbirth
  • Previous baby with low sugar, high bilirubin
  • Age over 35
  • Obesity
  • Repeated sugar on urine dip in pregnancy
  • Large amount of amniotic fluid on ultrasound
  • Certain ethnic groups (South Asian, Hispanic, Pacific Island, Aboriginal)

What is the treatment for gestational diabetes?

Most women can control their blood sugar with exercise and modifying their diet. Some women will require insulin to control their blood sugar. If you require insulin, you will be referred by the Diabetes Education Centre to an endocrinologist (a doctor who specialized in diabetes management).

Ways to treat gestational diabetes

  • Control your diet 
  • Exercise
  • Don’t gain an excessive amount of weight in pregnancy
  • Insulin if needed
  • Your care provider will arrange to have the baby’s growth followed with an ultrasound

What are the risks for untreated gestational diabetes?

Gestational diabetes is thought to be associated with an increased risk of:

  • Large baby over 4kg or 9lbs (macrosomia)
  • Shoulder dystocia
  • Stillbirth
  • Low sugar in the baby after birth
    • may need to bottle feed baby to avoid seizures

Carefully controlling your blood sugar may help decrease some of these risks.

What’s the problem with a large baby?

  • Large babies are more likely require a c-section or vacuum or forceps for delivery 
  • Associated with more maternal vaginal tearing
  • More likely to have a shoulder dystocia

What is shoulder dystocia?

Shoulder dystocia is when the baby’s head comes out, but the body gets stuck. This can be associated with nerve injury in the arm and very rarely with brain damage. Learn more about shoulder dystocia from the Royal College of Obstetricians & Gynaecologists. 

The diabetes doctor has recommended starting insulin. What should I do?

Insulin is safe in pregnancy and can help control your blood sugar and reduce some of the risks described above.

If you are started on insulin, let your doctor know. Pregnant women become diabetic in pregnancy because their placenta is making a hormone that makes it harder for them to metabolize sugar. If you find that you are on a certain dose of insulin and then the dose needs to be decreased, this could be a sign that the placenta is starting to get old and you should let your doctor know. It is okay if the insulin requirements keep going up.

It is generally recommended that if you have gestational diabetes requiring insulin, you should have labour induced at 38-39 weeks because of the risk of stillbirth after this. If you do not require insulin to control your sugar you probably do not need to be induced early. Speak to your care provider for more details.

What will happen after the baby is born?

You can stop sugar monitoring and/or insulin after the baby is born. Your family doctor will do another GCT about  three months after the baby is born to make sure that your sugar is normal again. Remember, even if the GCT after the baby is born is normal, you are still at a 10-50% higher risk in the future of diabetes. You can reduce this risk by exercising, eating a healthy diet and maintaining a healthy body weight.