Gestational diabetes mellitus (GDM) is a form of diabetes that develops during pregnancy, usually diagnosed between 24–28 weeks through an oral glucose tolerance test.
For most women, GDM resolves after birth. However, it serves as an important early warning sign for potential type 2 diabetes in the future. With proper management and support from your diabetes care team, you can have a healthy pregnancy and reduce risks for both you and your baby.
What you will learn in this fact sheet
This comprehensive guide provides essential information for managing gestational diabetes.
- Understanding GDM risk factors and why management matters.
- How to monitor blood glucose levels effectively.
- Nutrition strategies for managing blood glucose during pregnancy.
- What happens after delivery and reducing future diabetes risk.
Understanding gestational diabetes
What is GDM?
Gestational diabetes occurs when pregnancy hormones affect how your body uses insulin, leading to higher blood glucose levels. While GDM typically resolves after birth, it indicates increased risk of developing type 2 diabetes later in life.
Your diabetes care team will support you throughout your pregnancy. This team typically includes your obstetrician, diabetes nurse educator, dietitian and endocrinologist.
Risk factors for GDM
You're more likely to develop GDM if you are over 40 years old, have direct family members with type 2 diabetes, are of Aboriginal or Torres Strait Islander, Chinese, Indian, Middle Eastern, Polynesian or Melanesian background, have had GDM in another pregnancy, have had a baby weighing more than 4.5kg, gained excess weight early in pregnancy or were above healthy weight before pregnancy, have Polycystic Ovary Syndrome (PCOS), or take steroid or anti-psychotic medications.
Why management matters
Proper GDM management reduces risks including caesarean delivery, pre-term delivery, high blood pressure (pre-eclampsia), large birth weight, breathing difficulties after delivery and low blood glucose levels in your baby after birth.
Monitoring blood glucose levels
Blood glucose monitoring is essential for managing GDM. Your diabetes nurse educator will teach you how to use a glucometer and advise you of target levels during pregnancy.
When to check
Check four times each day until your baby is born: fasting (before eating breakfast), two hours after starting breakfast, two hours after starting lunch, and two hours after starting dinner.
Target blood glucose levels:
- Fasting or before breakfast: 4.0–5.0mmol/L.
- Two hours after meals: 4.0–6.7mmol/L.
If levels are too high
Contact your diabetes nurse educator or doctor if levels are above target. If no reason can be found and levels are higher than targets on two or more occasions at the same time of day, you'll likely be referred to an endocrinologist. Medication may be started to help lower blood glucose levels.
Nutrition management
A dietitian helps you learn how food choices achieve target blood glucose levels while maintaining health for you and your baby.
Understanding carbohydrates
Carbohydrates provide energy and break down into glucose during digestion, increasing blood glucose levels. The amount and type you eat affects blood glucose levels. Not eating enough carbohydrate can affect your baby's brain and nerve development, so include some carbohydrate at most meals and snacks each day.
Healthy carbohydrate choices include:
- wholegrain bread, crispbread and breakfast cereal
- grains such as barley, quinoa, pasta, noodles and rice
- lentils, legumes
- starchy vegetables (potato, sweet potato, corn)
- fruit
- milk, yoghurt.
Limit less healthy choices:
- biscuits, cakes, pastry
- sugar, honey, jam
- chocolate, confectionery
- regular soft drink, cordial and fruit juice
- potato crisps, corn chips.
Lower glycaemic index (GI) choices
Lower GI foods are digested more slowly, causing a gradual rise in blood glucose. Choose wholegrain and multigrain breads, rolled oats, long-grain rice (Basmati, Doongara), sweet potato, and most fruits. Your dietitian can provide detailed guidance on lower GI options.
Balanced meals and snacks
Use the plate method:
- Carbohydrate (¼ plate): portion size of your fist.
- Lean protein (¼ plate): portion size of your palm.
- Vegetables (½ plate): raw or cooked, portion size of two open hands.
- Add healthy fats like extra virgin olive oil and avocado.
- Drink plenty of water.
Healthy snacks
Eat snacks two hours after meals, after checking your blood glucose. Carbohydrate snack options include one piece of fruit, one small tub reduced-fat yoghurt, four Vita-Weat crackers with avocado or peanut butter, or one cup air-popped popcorn. Low-carbohydrate options include a small handful of nuts, hard-boiled egg, vegetable sticks, or small can of tuna.
Supporting vital diabetes research
This evidence-based fact sheet was developed by the Baker Heart and Diabetes Institute, where our team provides specialist care and support for women with gestational diabetes.
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Physical activity
30 minutes of physical activity is recommended each day unless advised otherwise by your doctor. Short walks after meals can help reduce blood glucose levels. Suitable activities include walking, swimming, aqua aerobics, pregnancy Pilates, bike riding and dancing. Jogging or higher-intensity physical activity should not be started during pregnancy.
Important pregnancy considerations
Healthy weight
Too much weight gain during pregnancy makes managing blood glucose levels more difficult and increases risk of birth complications. Discuss your individual weight gain expectations with your doctor.
Dietary supplements
A pregnancy-specific multivitamin is commonly recommended. Iron levels should be checked early in pregnancy and again around 28 weeks. A supplement containing at least 150µg iodine is recommended for most pregnant women in the third trimester.
Food safety
Avoid foods that may contain listeria during pregnancy, including soft cheeses, deli meats, pre-prepared salads, raw seafood and unpasteurised products. Choose freshly cooked foods and practice good food hygiene.
Other considerations
Not drinking alcohol is the safest option. Limit caffeine to 200mg or less per day. Artificial sweeteners like Equal, Splenda or Stevia are safe alternatives during pregnancy.
After delivery
What happens after birth
If you needed insulin or metformin during pregnancy, these are usually stopped once baby is born. Your healthcare team will advise how often to check blood glucose levels to confirm they've returned to a healthy range.
Blood glucose check
Have a repeat oral glucose tolerance test 6-12 weeks after delivery, then every 1-2 years. If planning another pregnancy, have an oral glucose tolerance test before conception and earlier during the pregnancy.
Breastfeeding
Having GDM doesn't stop you from breastfeeding. Breastfeeding provides complete nutrition for baby and offers benefits including protection against infections, reduced risk of obesity and diseases later in baby's life, weight management for mother, and reduced risk of breast and ovarian cancer for mother.
Reducing type 2 diabetes risk
Women who've had gestational diabetes are 10 times more likely to develop type 2 diabetes than women who didn't have GDM.
To reduce future risk:
- Follow a healthy balanced eating plan including vegetables, fruit, wholegrain bread and cereals, lean protein, reduced-fat dairy and healthy oils.
- Achieve and maintain a healthy body weight (breastfeeding can assist).
- Aim for at least 30 minutes of exercise per day including aerobic and strength training.
- Attend regular blood glucose screening tests.
Download your free fact sheet
Need personalised advice?
For individual guidance tailored to your pregnancy and health needs, make an appointment with an Accredited Practising Dietitian at the Baker Institute.
Contact our gestational diabetes service.