What is Gestational Diabetes?
• Gestational diabetes mellitus (GDM) is defined as any degree of glucose intolerance with onset or first recognition during pregnancy.
• It occurs when the body cannot produce enough insulin to meet the increased demands during pregnancy.
• Affects approximately 12-14% of Australian pregnancies, making it one of the most common pregnancy complications.
• Different from pre-existing diabetes as it develops specifically during pregnancy.
• Usually develops in the second or third trimester when pregnancy hormones interfere with insulin action.
• Most cases resolve after birth, though it increases the risk of developing type 2 diabetes later in life.
Risk Factors for Gestational Diabetes
Major Risk Factors:
• Age: Women over 35 years are at increased risk
• Family history: Having a parent or sibling with type 2 diabetes
• Previous GDM: History of gestational diabetes in previous pregnancies
• Previous macrosomia: Previously giving birth to a baby weighing over 4.5kg
• Ethnicity: Higher risk in Aboriginal and Torres Strait Islander women, women from Pacific Island, Indian subcontinent, Asian, Middle Eastern, or North African backgrounds
• Obesity: BMI over 30 kg/m² before pregnancy or excessive weight gain during pregnancy
Additional Risk Factors:
• Polycystic ovary syndrome (PCOS)
• Previous unexplained stillbirth or neonatal death
• Previous glucose intolerance
• Use of corticosteroid medications
• Hypertension or pre-eclampsia in current pregnancy
• Multiple pregnancy (twins, triplets)
Lower Risk Factors:
• Previous baby with birth defects
• Recurrent urinary tract infections during pregnancy
• Persistent glycosuria (glucose in urine)
Screening for Gestational Diabetes
Universal Screening Protocol:
• All pregnant women should be tested for gestational diabetes at 24-28 weeks of pregnancy (except those women who already have diabetes)
• Women who have risk factors for gestational diabetes should be tested earlier in their pregnancy
• Early screening is recommended at the booking visit (before 20 weeks) for high-risk women
Types of Screening Tests:
• Random plasma glucose: Initial screening tool, though not diagnostic
• Fasting plasma glucose: May be used for early screening in high-risk women
• 75g Oral Glucose Tolerance Test (OGTT): Gold standard diagnostic test
• HbA1c: May be used for early screening but not for diagnosis of GDM
Early Gestational Diabetes (eGDM):
- Early gestational diabetes (eGDM) is defined as glucose intolerance (but not meeting the criteria for other forms of diabetes) that was diagnosed before 20 week’s gestation
- Requires early screening and different management approach
- Often indicates pre-existing insulin resistance
Diagnosis of Gestational Diabetes
Current Australian Diagnostic Criteria (ADIPS 2025):
Irrespective of gestation, gestational diabetes mellitus should be diagnosed using one or more of the following criteria during a 75 g two-hour POGTT: (i) FPG ≥ 5.3-6.9 mmol/L; (ii) one-hour plasma glucose (1hPG) ≥ 10.6 mmol/L; (iii) 2hPG ≥ 9.0-11.0 mmol/L
Diagnostic Process:
• Preparation: Fast for 8-12 hours before the test
• Baseline: Fasting plasma glucose measurement
• Glucose load: Drink 75g glucose solution
• Monitoring: Blood glucose measured at 1 hour and 2 hours post-glucose load
• Diagnosis: Only one abnormal value needed for GDM diagnosis
Interpretation of Results:
• Normal: Fasting <5.1 mmol/L, 1-hour <10.0 mmol/L, 2-hour <8.5 mmol/L (note: these are older criteria; current ADIPS 2025 criteria are stricter)
• GDM: Any one value meeting the diagnostic thresholds listed above
• Overt diabetes: Fasting glucose ≥7.0 mmol/L or 2-hour glucose ≥11.1 mmol/L
Management of Gestational Diabetes
Initial Management Steps:
• Referral to diabetes educator and dietitian within 1-2 weeks of diagnosis
• Education about GDM, its implications, and management strategies
• Blood glucose monitoring equipment and training provided
• Regular obstetric and endocrine follow-up scheduled
• Development of individualized management plan
Blood Glucose Monitoring:
• Frequency: Usually 4 times daily (fasting and 1-2 hours after each meal) • Target levels:
- Fasting: <5.0 mmol/L
- 1-hour post-meal: <7.4 mmol/L
- 2-hour post-meal: <6.7 mmol/L
- Documentation: Maintain detailed logbook of readings, food intake, and activities
- Review: Weekly review of glucose patterns with healthcare team
Medical Monitoring:
• Fortnightly appointments with obstetrician and diabetes team
• Monthly growth scans from 28 week’s gestation
• Regular blood pressure monitoring
• Urinalysis for protein and ketones
• Fetal wellbeing assessments including CTG monitoring from 38 weeks
Dietary Management
Basic Dietary Principles:
• If you have gestational diabetes, a healthy diet will usually involve spreading out your carbohydrate intake over 3 small meals and 2 to 3 snacks each day.
• Focus on complex carbohydrates with a low glycemic index
• Adequate protein at each meal and snack
• Include healthy fats in moderation
• Maintain appropriate weight gain during pregnancy
Carbohydrate Management:
• Distribution: Spread carbohydrates evenly throughout the day
• Type: Choose wholegrain, high-fiber options
• Portion control: Use carbohydrate counting techniques
• Timing: Consistent meal and snack times
• Quality: Avoid refined sugars and processed foods
Recommended Foods:
• Proteins: Lean meats, poultry, fish, eggs, legumes, tofu
• Carbohydrates: Wholegrain breads, brown rice, quinoa, oats
• Vegetables: Non-starchy vegetables, leafy greens
• Fruits: Fresh fruits in controlled portions
• Dairy: Low-fat milk, yoghurt, cheese
• Fats: Nuts, seeds, avocado, olive oil
Foods to Limit or Avoid:
• Sugary drinks and fruit juices
• Refined cereals and white bread
• Sweets, cakes, and desserts
• Fast food and processed meals
• Large portions of fruit
• High-glycemic index foods
Professional Support:
• Your doctor or midwife will usually refer you to a dietitian who can give you personalized advice about your diet and lifestyle
• Regular dietary reviews and adjustments
• Cultural and personal food preferences considered
• Practical meal planning assistance provided
Exercise and Lifestyle Management
Exercise Recommendations:
• Frequency: 30 minutes of moderate exercise on most days
• Types: Walking, swimming, pregnancy yoga, stationary cycling
• Intensity: Should be able to hold a conversation while exercising
• Safety: Avoid contact sports and activities with fall risk
• Monitoring: Check blood glucose before and after exercise
Lifestyle Modifications:
• Maintain regular sleep patterns
• Stress management techniques
• Avoid smoking and alcohol
• Regular medical appointments and monitoring
• Social support and family involvement
Medical Treatment Options
When Medication is Needed:
• Blood glucose targets not met with diet and exercise after 1-2 weeks
• Fasting glucose consistently >5.0 mmol/L
• Post-meal glucose consistently above targets
• Evidence of excessive fetal growth on ultrasound
• Maternal complications developing
Insulin Therapy:
• First-line medication: Safe and effective during pregnancy
• Types: Usually intermediate-acting and rapid-acting insulin
• Administration: Multiple daily injections typically required
• Adjustment: Doses adjusted based on blood glucose patterns
• Education: Comprehensive training on injection technique and storage
Metformin:
• Second-line option when insulin is refused or unsuitable
• May be used in combination with insulin
• Crosses placenta but appears safe in pregnancy
• Regular monitoring required
• Not suitable for all women with GDM
Alternative Medications:
• Glyburide may be considered in specific circumstances
• Most other diabetes medications contraindicated in pregnancy
• Decision made by specialist diabetes team
• Individual risk-benefit assessment required
Complications and Risks
Maternal Complications:
• Short-term: Increased risk of caesarean section, pregnancy-induced hypertension, pre-eclampsia
• Long-term: 50% risk of developing type 2 diabetes within 10 years
• Future pregnancies: Increased risk of recurrent GDM (up to 68%)
• Cardiovascular: Higher risk of heart disease later in life
Fetal and Neonatal Complications:
• Macrosomia: Large babies (>4.5kg) leading to birth complications
• Hypoglycaemia: Low blood sugar in newborn requiring treatment
• Respiratory distress: Breathing difficulties at birth
• Jaundice: Higher bilirubin levels requiring phototherapy
• Birth injuries: Shoulder dystocia, fractures, nerve damage
Long-term Child Health Risks:
• Increased risk of childhood obesity
• Higher likelihood of developing type 2 diabetes
• Metabolic syndrome in adolescence and adulthood
• Potential neurodevelopmental impacts
Minimizing Risks:
• Strict blood glucose control during pregnancy
• Regular monitoring and medical care
• Appropriate timing and mode of delivery
• Immediate postnatal glucose monitoring for baby
• Long-term health surveillance for mother and child
Birth Planning and Delivery
Delivery Timing:
• Most women can deliver at term (39-40 weeks)
• Earlier delivery may be recommended if complications arise
• Individual assessment based on maternal and fetal wellbeing
• Continuous glucose monitoring during labour
• IV insulin infusion may be required during labour
Mode of Delivery:
• Vaginal delivery preferred when possible
• Caesarean section rates are higher in GDM
• Decision based on estimated fetal weight and maternal factors
• Shoulder dystocia risk considered in delivery planning
• Paediatric team available at delivery
Immediate Postnatal Care:
• Maternal blood glucose monitoring continued initially
• Insulin requirements drop dramatically after delivery
• Baby's blood glucose checked regularly in first 24-48 hours
• Breastfeeding encouraged and supported
• Early skin-to-skin contact promoted
Postpartum Follow-up and Long-term Care
Immediate Postpartum (0-6 weeks):
• Blood glucose monitoring ceased unless diabetes persists
• Breastfeeding support and encouragement
• Contraception counselling and family planning
• Diet and exercise advice for gradual weight loss
• Mental health screening and support
6-12 Weeks Postpartum Testing:
• 75g OGTT: Essential screening for persistent diabetes
• Timing: Performed 6-12 weeks after delivery
• Interpretation:
- Normal: Fasting <7.0 mmol/L and 2-hour <7.8 mmol/L
- Impaired glucose tolerance: 2-hour 7.8-11.0 mmol/L
- Diabetes: Fasting ≥7.0 mmol/L or 2-hour ≥11.1 mmol/L
- Follow-up: Results determine ongoing care pathway
Long-term Monitoring:
• Annual screening: HbA1c or fasting glucose
• Lifestyle counselling: Ongoing diet and exercise support
• Weight management: Achieving and maintaining a healthy BMI
• Cardiovascular risk: Blood pressure and cholesterol monitoring
• Family planning: Preconception counselling for future pregnancies
Prevention of Type 2 Diabetes:
• Maintain a healthy weight through diet and exercise
• Regular physical activity (150 minutes per week)
• Mediterranean-style diet with low glycemic index foods
• Avoid excessive weight gain between pregnancies
• Consider diabetes prevention programs if available
• Regular health checks and screening
Future Pregnancy Planning:
• Preconception counselling and optimisation
• Earlier GDM screening in subsequent pregnancies
• Folic acid supplementation
• Healthy lifestyle establishment before conception
• Blood glucose targets optimised if diabetes has developed
Support and Resources
Australian Support Services:
• Diabetes Australia: National support and information service
• NDSS (National Diabetes Services Scheme): Subsidised products and education
• Australian Breastfeeding Association: Breastfeeding support for women with GDM
• Beyond Blue: Mental health support during and after pregnancy
Healthcare Team:
• Obstetrician or midwife for pregnancy care
• Endocrinologist or diabetes specialist
• Diabetes educator for ongoing education and support
• Dietitian for nutritional counselling
• General practitioner for coordinated care
Educational Resources:
• ADIPS (Australasian Diabetes in Pregnancy Society) guidelines and information
• Diabetes Australia fact sheets and educational materials
• Hospital-based diabetes education programs
• Online resources and support groups
• Culturally appropriate resources for diverse communities
Financial Support:
• Medicare rebates for diabetes educator and dietitian consultations
• NDSS subsidised blood glucose monitoring supplies
• Private health insurance may cover additional services
• Some states provide additional support programs
This comprehensive guide provides evidence-based information about gestational diabetes management in Australia. Always consult with your healthcare team for personalized advice and treatment plans tailored to your specific circumstances and needs.