Understanding gestational diabetes

What gestational diabetes is, why it happens in pregnancy, how it's tested for, what it can mean for you and your baby, and why treatment makes a real difference.

6 min read · last reviewed October 3, 2026

Finding out you have diabetes while you're pregnant can be a real shock. You may worry about your baby, feel guilty, or wonder how you'll manage one more thing. These feelings are completely normal.

Here's what's most important to know: gestational diabetes is common, it's not your fault, and it can be managed. With the right care, most people with gestational diabetes have healthy pregnancies and healthy babies. This guide explains what's happening and why treatment matters.

What is gestational diabetes?

Gestational diabetes is high blood sugar that's first found during pregnancy, usually in the second half.

Here's why it happens. Your body uses a hormone called insulin, made by your pancreas, to move sugar (glucose) from your blood into your cells. During pregnancy, the placenta, which feeds your baby, makes hormones that help your baby grow. These hormones also make insulin work less well. This is a normal part of pregnancy.

To keep up, most people's bodies make two to three times more insulin than usual. In gestational diabetes, the body can't make quite enough extra insulin, so blood sugar rises.

It's not caused by eating too much sugar, and it's not something you did wrong. It's mainly about pregnancy hormones and how your body responds to them.

How common is it?

Very common. Diabetes Canada says between 3% and 20% of pregnant people develop gestational diabetes, depending on their risk factors.

Who is more likely to get it?

Anyone can get gestational diabetes, but it's more likely if you:

• are 35 or older
• have a parent, brother or sister with type 2 diabetes
• are of South Asian, Asian, African, Caribbean, Hispanic, Middle Eastern or Indigenous heritage
• had gestational diabetes in a past pregnancy, or a baby who weighed more than 4 kg (9 lb)
• have polycystic ovary syndrome (PCOS)
• had prediabetes before pregnancy
• carry extra weight
• are taking certain medicines, such as steroids

Many of these are outside your control.

How is it tested?

Gestational diabetes usually has no symptoms, so testing is offered to pregnant people, most often between 24 and 28 weeks. If you have risk factors, your provider may test you earlier in pregnancy, too.

The tests use a sugary drink and blood tests. In Canada, Diabetes Canada's preferred approach usually starts with a screening test: you drink a sugary drink (no fasting needed) and have a blood test an hour later. If the result is high, you have a longer glucose tolerance test: you fast overnight, have a blood test, drink a sugary drink, and have more blood tests over 2 hours. Some clinics go straight to the longer test. Your provider will explain which test you'll have.

Something you can do today: Ask your provider for your test results and what they mean.

Why does treatment matter?

When blood sugar stays high during pregnancy, extra sugar crosses the placenta to your baby. Your baby's body makes extra insulin to handle it, which can cause the baby to grow larger than usual and store extra fat.

Without treatment, gestational diabetes can raise the chances of:

For your baby:

• growing very large, which can make birth harder and raise the risk of injury during birth
• low blood sugar right after birth
• jaundice (yellow skin) and breathing problems after birth
• a higher chance of weight problems and type 2 diabetes later in life

For you:

• high blood pressure and preeclampsia during pregnancy
• needing a caesarean birth (C-section)
• developing type 2 diabetes later in life

That list can feel scary. But here's the hopeful part: treatment works. Two large studies, in Australia and the U.S., found that treating gestational diabetes lowered the chances of serious problems for babies, of babies growing very large, and of preeclampsia. Every reading in your target range helps.

What are the targets?

Your team will set your targets. Diabetes Canada suggests these for most people with gestational diabetes:

• fasting (before breakfast): below 5.3 mmol/L (about 95 mg/dL)
• 1 hour after starting a meal: below 7.8 mmol/L (about 140 mg/dL), or
• 2 hours after starting a meal: below 6.7 mmol/L (about 120 mg/dL)

Other countries use similar numbers. Your team will tell you which after-meal check to use.

Will it go away?

For most people, blood sugar returns to normal soon after the baby is born, once the placenta is delivered. But having had gestational diabetes means a higher chance of type 2 diabetes later, and of gestational diabetes in a future pregnancy. Read After baby is born to learn about the follow-up tests that protect your long-term health.

Sometimes, testing in pregnancy finds diabetes that was there before pregnancy but hadn't been diagnosed. Your team will check for this after the birth.

Something you can do this week: Write down one or two questions that are worrying you, and ask them at your next visit.

Questions to ask your care team

• What were my test results?
• What are my blood sugar targets, and when should I check?
• Can I see a dietitian and a diabetes educator?
• How will you check on my baby's growth?
• Does this change my birth plan?
• What happens after my baby is born?

This article is general information, not medical advice. Talk with your health care team about your own situation. In an emergency, call 9-1-1 or your local emergency number.

In an emergency, call 9-1-1 or your local emergency number.

General information, not medical advice. It does not replace your own care team. If you think you or someone else is having a medical emergency, call 9-1-1 or your local emergency number. If you are in crisis or thinking about suicide, call or text 9-8-8 (Canada and the US).

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