Receiving a diagnosis of gestational diabetes, or pregnancy diabetes, can be a source of concern for expectant mothers and their loved ones. However, this condition affects between 3% and 20% of pregnant women, depending on the criteria used.

What is gestational diabetes?

During pregnancy, hormones change the way the body manages blood sugar. Gestational diabetes is a reduced tolerance to glucose, causing high blood sugar levels (hyperglycemia), first detected during pregnancy. The pancreas does not produce enough insulin to compensate for this increase.

Changes throughout pregnancy

The first trimester

At the beginning of pregnancy, insulin production often increases, which can lower blood sugar levels. This sometimes causes fatigue, dizziness, hunger, excessive thirst, irritability, headaches, and frequent urination.

Glucose is the baby’s main source of fuel, transmitted through the placenta, but maternal insulin does not cross the placenta. From 10 weeks onwards, the baby produces its own insulin to manage the glucose it receives. If the mother’s blood sugar level rises, the baby’s blood sugar level also rises, which stimulates its insulin production.

Second and third trimesters

In the second trimester, hormones make the body less sensitive to insulin, which naturally increases blood sugar levels. This adaptation aims to provide more glucose to the baby.

The maternal pancreas must produce up to three times more insulin to compensate. If this mechanism is not sufficient, gestational diabetes is diagnosed.

Screening

Between 24 and 28 weeks, a screening test involves drinking a beverage containing 50 g of glucose, followed by a blood test after one hour. If blood sugar levels exceed the thresholds, an OGTT (oral glucose tolerance test) is recommended.

The OGTT

The diagnostic test for gestational diabetes is called the OGTT (oral glucose tolerance test). The pregnant woman must fast and drink a liquid containing 75 or 100 g of glucose, depending on the prescription. Two blood samples are then taken: one after 1 hour and a second after 2 hours, in order to assess whether the pancreas is producing enough insulin to control blood sugar levels.

Before the test, the woman must maintain a normal diet and activity level for at least 3 days. Caffeine should be avoided, as it can increase blood sugar levels.

The OGTT is the gold standard test for diagnosis. If two results exceed the established thresholds, gestational diabetes is confirmed. For example:

• Fasting blood sugar > 7 mmol/L
• Blood sugar 2 hours after 75 g of glucose > 11.1 mmol/L
• Random blood sugar (regardless of meal time) > 11.1 mmol/L

If only one result is abnormal, it is referred to as glucose intolerance.

Capillary blood glucose test

Another screening tool is the capillary blood glucose test. The pregnant woman is asked to measure her blood glucose by pricking her fingertip four times a day for a week: in the morning on an empty stomach, then one hour after each meal.

The results are recorded in a logbook to be analyzed with a healthcare professional. The targets to be met are generally:

• Fasting: between 3.5 and 5.2 mmol/L
• One hour after a meal: between 7.1 and 7.7 mmol/L

This daily monitoring allows blood sugar fluctuations to be observed over a longer period of time, providing a more complete picture of blood sugar control.

Classification of gestational diabetes

Class A-1

Class A-1 gestational diabetes affects pregnant women with abnormal HGPO test results but normal fasting blood sugar levels. Medical follow-up with a doctor, endocrinologist, and nutritionist is then put in place to balance the diet and stabilize blood sugar levels.

In most cases, an appropriate diet is sufficient, adjusted as insulin resistance increases during pregnancy.

Class A-2

Class A-2 gestational diabetes affects 20% of pregnant women with gestational diabetes. These women must take medication to maintain their blood sugar levels. In this class, dietary changes alone are not sufficient to stabilize the situation.

Treatment and follow-up

Treatment and follow-up for gestational diabetes is carried out on several levels.

Alimentation :

Diet is the most important factor in treating gestational diabetes. A nutritionist will help you calculate your daily calorie intake and recommendations based on your age, weight, medical history, blood sugar levels, etc.

Exercise:

Exercise helps lower blood sugar levels in pregnant women, as muscles use sugar during activity, which in turn reduces the demand for insulin.

Staying active therefore helps to better control blood sugar levels during pregnancy. Aerobic and muscle-building exercises should be part of your daily routine. However, be careful not to exercise too intensely or for too long. Snacks may be necessary.

Capillary blood glucose monitoring:

Frequent blood glucose measurements four times a day allow the balance between sugar and insulin in the pregnant woman’s blood to be monitored. This is often done in the morning on an empty stomach, then one hour after meals and sometimes more, depending on each individual’s situation.

Medication:

For women who need it, oral medication or insulin injections may be necessary to maintain the correct blood sugar balance and prevent complications that could otherwise arise.

Monitoring:

• Fetal monitoring at least twice a week from 32 weeks of pregnancy.
• Frequent ultrasounds may be performed to monitor the baby’s weight.
• Induction may be possible before 40 weeks to prevent potential complications at the end of pregnancy.
• A cesarean section is only indicated if the mother’s condition does not allow for vaginal delivery.

Protective factors for gestational diabetes screening

• Being under 25 years of age
• Being of Caucasian (white) ethnicity
• Having a body mass index below 27
• Having no family history of gestational diabetes or glucose intolerance
• Having no family history of diabetes in first-degree relatives (father, mother, brother, sister).

Risk factors for developing gestational diabetes

• Previous history of gestational diabetes
• Being over 35 years of age
• Having a body mass index over 30 (overweight)
• Twin pregnancy
• Close family member with type 2 diabetes
• Known to have polycystic ovaries
• Gave birth to a very large baby (macrosomia at birth)
• Being treated with certain medications, mainly cortisone-based
• Being part of the higher-risk population: Hispanic, Asian, and African.

Possible complications of gestational diabetes

Possible complications of gestational diabetes can affect both the baby and the mother.

In the baby:

• More congenital abnormalities for the baby when there is pre-existing diabetes (before pregnancy), such as 7 to 10% of heart defects, cardiomyopathy, musculoskeletal and neurological disorders. However, in the case of gestational diabetes, there is no evidence of a risk of congenital abnormalities in the baby, given that diabetes most often occurs at the end of pregnancy and the baby is already well advanced in its development in utero
• Frequent hypoglycemia in the postnatal period
• Breathing difficulties at birth
• 1/3 risk of recurrence in a subsequent pregnancy
• In 15 to 30% of cases: macrosomic baby, i.e., larger than average
• Childbirth is often more traumatic, mostly due to the baby’s weight
• Prematurity
• More jaundice
• Death in utero (very rare complication with monitoring care)

To monitor later in life:

• Obesity
• Diabetes

In the mother:

• Having more amniotic fluid (polyhydramnios)
• Risk of high blood pressure and preeclampsia
• Risk of obesity later in life
• In 10 to 60% of cases, increased risk of developing diabetes within 20 years

And after delivery?

Blood sugar monitoring is recommended between 6 and 12 weeks after birth (or after breastfeeding). The woman will then repeat the OGTT (75 g of glucose) to check whether her levels have returned to normal.

In summary, gestational diabetes is a complex condition. This article aims to provide a better understanding of it, without going into the medical details specific to each situation. If the results are uncertain or cause for concern, personalized follow-up with healthcare professionals will be offered to provide compassionate support to the mother-to-be throughout her pregnancy—and beyond.

The important thing is to do your best, one day at a time.

Marie Fortier
The baby expert

Updated: April 2025.

References : 

• Diabète Québec. (2024). Diabète de grossesse. Repéré le 8 avril 2025 à https://www.diabete.qc.ca/le-diabete/informations-sur-le-diabete/diabete-de-grossesse/

• CHU Sainte-Justine. (2022). Bien vivre sa grossesse avec un diabète de grossesse [Dépliant]. Repéré le 8 avril 2025 à https://www.chusj.org/getmedia/0b75e5b2-78c9-4244-9796-8ada59cf58f7/depliant-F-4203-Bien-vivre-sa-grossesse-avec-le-diabete-gestationnel_web.pdf.aspx?ext=.pdf

• CHU de Québec – Université Laval. (2025). Diabète de grossesse. Repéré le 8 avril 2025 à https://www.chudequebec.ca/patient/maladies-soins-et-services/m-informer-sur-ma-maladie-ou-ma-condition/diabete-de-grossesse.aspx

• Société des obstétriciens et gynécologues du Canada (SOGC). (2019). Directive clinique n° 393 – Le diabète pendant la grossesse. Repéré le 8 avril 2025 à https://www.jogc.com/article/S1701-2163(19)30448-7/abstract

• Lowdermilk, D. L., Perry, S. E., & Cashion, K. (s.d.). Soins infirmiers en périnatalité (2e éd.). Montréal, QC : Chenelière Éducation.