Gestational Diabetes

Gestational diabetes (GDM) is a condition of hyperglycemia (high blood glucose) first identified in pregnancy. During pregnancy, the hormones produced by the placenta cause  insulin resistance, so the body cannot use insulin properly. This leads to elevated blood glucose levels and requires the pancreas to produce extra insulin.

In gestational diabetes, the pancreas cannot produce extra insulin and the blood glucose levels remain elevated.

Risk factors

  • Obesity (Body Mass Index 30 kg/m2 or higher)
  • Being from a high risk group (African, Arab, Asian, Hispanic, Indigenous, South Asian)
  • Age 35 years or older
  • Using corticosteroid medication
  • Having prediabetes
  • Having had previous GDM
  • Having a baby weighing greater than 4 kg
  • Having a parent, brother or sister with Type 2 diabetes
  • Having Polycystic Ovarian Syndrome or Acanthosis Nigricans


Symptoms are non-specific and may include fatigue and frequent urination. 


Women who are pregnant should be screened for GDM between 24-28 weeks’ gestation. For individuals with several of the above risk factors, screening should be done in the first trimester and in subsequent trimesters if negative. The OGCT (Oral Glucose Challenge Test) is used to diagnose GDM. Women are given a 50g glucose drink, followed by a plasma glucose test taken 1 hour after.  

An oral glucose tolerance test (OGTT) may be required if the OGCT is not diagnostic. 

If not treated, GDM increases the risk for a large for gestational age baby, hypoglycemia at birth and higher rates of caesarian section. The baby will not be born with diabetes, however may be at risk for future diabetes due to lifestyle choices such as inactivity or an unhealthy diet.


Treatment usually includes following a carbohydrate managed diet with 3 meals and at least 3 snacks and daily blood glucose monitoring.

Regular activity (e.g., walking for 30 minutes per day, 5 days per week) is recommended to assist with good blood glucose management, as long as there are no contraindications (e.g., vaginal bleeding, severe high blood pressure).

Women with gestational diabetes are at risk for future diabetes. It is recommended to follow up with an OGTT within 6 months to check whether diabetes is still present.

Was this page helpful?

If you would like us to follow-up with you to provide assistance, please enter your preferences for how you wish to be contacted below:


Personal information is collected under the authority of the Public Hospitals Act R.S.O. 1990, CHAPTER P.40 for the purpose of contacting the sender in response to an inquiry. If you have questions about the collection of this information, please contact a Privacy and Freedom of Information Consultant, Mount Hope Centre for Long Term Care, 21 Grosvenor Street, Room WB31, London Ontario, N6A 1Y6. Phone: 519-646-6100 ext. 64545.