Gestational Diabetes in Pregnancy: Risks, Testing and How to Protect Your Baby
Gestational diabetes is a common pregnancy complication. In Australia, it affects a significant number of women each year, including many who have otherwise experienced a straightforward pregnancy.
A diagnosis can cause concern. However, with appropriate monitoring and management, most women with gestational diabetes go on to have healthy pregnancies and healthy babies.
This article explains what gestational diabetes is, how it is diagnosed in Australia, the potential risks and how it is managed.
What is gestational diabetes?
Gestational diabetes mellitus is a form of diabetes that develops during pregnancy. It occurs when the body is unable to produce enough insulin to manage increased blood sugar levels caused by pregnancy hormones.
During pregnancy, hormones produced by the placenta create insulin resistance. This ensures adequate glucose supply to the growing baby. In some women, the pancreas cannot produce sufficient insulin to compensate for this resistance. As a result, blood glucose levels rise.
Gestational diabetes is different from type 1 and type 2 diabetes. It develops during pregnancy and in most cases resolves after birth.
Who is at risk of gestational diabetes?
Gestational diabetes can occur in any pregnancy. However, certain factors increase risk:
Age over 35
Family history of type 2 diabetes
Previous gestational diabetes
Previous baby weighing more than 4 kilograms
Polycystic ovarian syndrome
Higher body mass index
Certain ethnic backgrounds (eg South Asian, Southeast Asian, Pacific Islands)
Because some women without clear risk factors still develop gestational diabetes, universal screening is recommended in Australia.
How is gestational diabetes diagnosed in Australia?
Screening usually occurs between 24 and 28 weeks of pregnancy. Women at higher risk may be tested earlier.
The 75g oral glucose tolerance test
The standard diagnostic test is the 75 gram oral glucose tolerance test. This involves:
Fasting overnight
A fasting blood test
Drinking a glucose solution
Blood tests at one hour and two hours
The results indicate how effectively the body processes glucose. If one or more values exceed established thresholds, gestational diabetes is diagnosed.
Although the test can be inconvenient, it allows early identification and management before complications arise.
Why is gestational diabetes important?
Elevated maternal blood glucose levels result in increased glucose crossing the placenta. The baby produces more insulin in response. This can affect fetal growth and metabolism.
Potential risks for the baby
Increased birth weight, also known as macrosomia
Shoulder dystocia during delivery
Neonatal hypoglycaemia after birth
Increased likelihood of special care nursery admission
Increased risk of later metabolic disease
Potential risks for the mother
Higher risk of pre-eclampsia
Increased likelihood of induction of labour
Increased caesarean section rates
Greater long term risk of type 2 diabetes
It is important to emphasise that these risks are significantly reduced when blood glucose levels are well controlled.
Is gestational diabetes considered a high risk pregnancy?
Gestational diabetes places a pregnancy into a higher risk category because it requires additional monitoring.
This typically includes:
More frequent antenatal visits
Regular blood glucose monitoring
Growth ultrasounds to assess fetal size
Careful planning around timing of delivery
The aim is early identification of any changes in maternal or fetal wellbeing.
How is gestational diabetes managed?
Management depends on blood glucose levels and individual clinical factors.
Dietary management
For many women, gestational diabetes can be managed with dietary adjustments. This generally involves:
Reducing simple sugars
Distributing carbohydrate intake evenly through the day
Combining carbohydrates with protein
Avoiding large glucose spikes
Referral to a diabetes specialist experienced in pregnancy is often helpful.
Blood glucose monitoring
Women are usually advised to monitor their blood glucose levels at home. This commonly includes:
A fasting reading in the morning
Readings one or two hours after meals
These measurements guide ongoing management decisions.
Physical activity
Moderate physical activity, such as walking after meals, can improve insulin sensitivity and help stabilise blood glucose levels.
Medication or insulin
If diet and exercise are insufficient to maintain target glucose levels, medication or insulin may be recommended. Insulin is safe in pregnancy and does not cross the placenta. Its purpose is to maintain stable maternal blood sugar levels and reduce risks to the baby.
Treatment decisions are individualised based on clinical assessment.
Does gestational diabetes change delivery planning?
Gestational diabetes may influence decisions about timing and mode of delivery. Although for most women with mild gestational diabetes and good blood sugar control timing and mode of birth are not usually affected.
If blood glucose levels are well controlled and fetal growth remains within normal limits, vaginal birth is often appropriate.
If the baby is measuring significantly large or if other complications develop, induction of labour or caesarean section may be recommended. These decisions are based on balancing maternal and fetal risks.
Delivery planning is guided by ongoing assessment throughout the pregnancy and careful discussion based on the wishes of the pregnant woman.
What happens after birth?
In most cases, blood glucose levels return to normal shortly after delivery.
However, follow up is important. This includes:
A repeat glucose tolerance test approximately 6 to 12 weeks postpartum
Ongoing monitoring of long term metabolic health
Women who have had gestational diabetes have an increased lifetime risk of developing type 2 diabetes. Maintaining a healthy lifestyle after pregnancy can reduce this risk.
Breastfeeding is encouraged where possible, as it has metabolic benefits for both mother and baby.
Can gestational diabetes be prevented?
There is no guaranteed way to prevent gestational diabetes. However, maintaining a healthy weight, engaging in regular physical activity and managing underlying conditions such as polycystic ovarian syndrome before pregnancy may reduce risk.
Pre pregnancy consultation can be helpful for women with known risk factors.
When should you seek specialist advice?
You should seek specialist obstetric advice if:
You have been diagnosed with gestational diabetes
You had gestational diabetes in a previous pregnancy
You have additional risk factors such as PCOS or insulin resistance
You have concerns about fetal growth
You would like individualised guidance regarding management and delivery planning
Early assessment allows structured monitoring and coordinated care.
About Dr Greg Jenkins
Dr Greg Jenkins is a specialist obstetrician and gynaecologist and Head of Obstetrics and Gynaecology at Westmead Public Hospital. He provides obstetric, fertility and gynaecological care in Western Sydney and delivers at Norwest Private, Westmead Private and Westmead Public Hospitals.
Appointments: 02 8805 7900
