What is gestational diabetes?

Gestational diabetes is a type of diabetes that is found during pregnancy. It's different to having pre-existing diabetes in pregnancy.

If you have gestational diabetes, you will have higher-than-normal levels of sugar in your blood. This can be unhealthy for both you and your baby.

Around 1 in 10 pregnancies are affected by gestational diabetes.

What are the symptoms of gestational diabetes?

Often, gestational diabetes doesn't cause any symptoms. It is diagnosed with routine antenatal screening.

You might experience symptoms of high blood sugar, like increased thirst and frequent urination.

What causes gestational diabetes?

When you are pregnant, your placenta produces hormones to help your baby grow. These hormones also reduce the action of insulin in your body. This is known as insulin resistance.

Your body will make more insulin during pregnancy.

If you already have insulin resistance, your body may not be able to cope with this extra need for insulin. This can lead to gestational diabetes.

You are at higher risk of developing gestational diabetes if you:

• are above a healthy weight range during pregnancy
• are over 40 years old
• have a family history of type 2 diabetes
• were diagnosed with gestational diabetes or had a large baby in a previous pregnancy
• have polycystic ovary syndrome
• are taking some types of antipsychotic or steroid medicines

You may also have an increased risk of gestational diabetes if you come from certain ethnic backgrounds. These backgrounds include:

• South East Asian
• Middle Eastern
• Pacific Islander
• African
• Aboriginal and/or Torres Strait Islander

When should I see my doctor?

You should see your doctor or midwife for regular antenatal appointments during your pregnancy. Gestational diabetes can be diagnosed at these appointments.

How is gestational diabetes diagnosed?

Screening for gestational diabetes is recommended in all pregnancies.

There are two tests used in Australia to screen for gestational diabetes. These are the:

• glycated haemoglobin (HbA_1c) test
• oral glucose tolerance test (OGTT)

If you are pregnant, it is recommended that you have:

• an HbA1c test done in the first trimester of your pregnancy — if you have a higher risk of high blood sugar
• an OGTT before week 20 of your pregnancy — if you have a history of gestational diabetes or based on your first trimester HbA_1c
• an OGTT between 24 and 28 weeks of pregnancy — all pregnancies

It is your choice whether you are tested for gestational diabetes or not. If you are not sure about having a test, speak to your doctor or care provider. They can answer your questions and give you advice. Discussing your options with your doctor or midwife can help you be involved in shared decisions.

Glycated haemoglobin (HbA1c) test

This is a blood test that measures the glucose inside your red blood cells. This can help your doctor understand your blood sugar levels over the last 2 to 3 months.

You usually don't need to prepare for an HbA1c test. This means you do not have to fast.

If you have iron deficiency or thalassemia, this test may not be suitable for you.

Oral glucose tolerance test (OGTT)

You need to fast for 8 to 10 hours before having an OGTT. You may choose to fast (not eat anything) overnight and miss breakfast.

First, you will have a blood test to check your baseline blood sugar level. Then you will be given a drink that contains 75 grams (g) of glucose. Another blood sample is taken for testing after 1 hour and 2 hours. You will usually need to stay at the laboratory for the full duration of the test. The test provides 3 measurements of your blood sugar level, at:

• baseline
• 1 hour after drinking 75g of glucose
• 2 hours after drinking 75g of glucose

If one of these 3 measurements is higher than the laboratory range, you will be diagnosed with gestational diabetes.

How is gestational diabetes managed?

If you have gestational diabetes, you may need more frequent antenatal appointments. This can help monitor your blood sugar.

Your doctor can give you important health advice about how to manage your blood glucose levels. This may include monitoring your blood sugar levels at home.

Managing gestational diabetes can reduce the chance of complications for both you and your baby.

For more support, your doctor may refer you to:

• an obstetrician
• a dietitian
• a diabetes educator

Blood glucose monitoring

If you have gestational diabetes, you will need to check and record your blood glucose at least 4 times a day. You can record your blood glucose straight after waking up, and either 1 or 2 hours after each main meal.

Your healthcare team can teach you how to check your blood glucose at home. This is done using a with a blood glucose meter (glucometer). Your healthcare team can give you a target range for your blood glucose levels. In Australia, the target blood glucose levels are commonly set at:

• 5.0mmol/L or less before breakfast
• 7.4mmol/L or less, if you test one hour after starting your meal
• 6.7mmol/L or less, if you test 2 hours after starting your meal

Depending on your situation, your doctor or diabetes nurse educator might set different targets.

A healthy diet

If you have gestational diabetes, a healthy diet is important.

In pregnancy, it is recommended to have over 3 small meals and 2 to 3 snacks each day.

Your doctor or midwife will usually refer you to a dietitian who can give you personalised advice about your diet and lifestyle.

Exercise

Moderate levels of physical activity can help you manage your blood glucose levels. Moderate physical activity raises your breathing or heart rate. This includes:

• walking
• swimming
• riding a bike

Always check with your doctor first before you start exercising while you are pregnant.

Medicine

Sometimes your blood sugar levels may stay high even after changing your diet and increasing your levels of physical activity. If so, you can ask your doctor about medicines. They can discuss the most appropriate treatment for you.

Insulin injections are considered safe to take during pregnancy. If you need to use insulin, you may be referred to a diabetes nurse educator who will teach you how to safely inject insulin.

Metformin pills also appear to be safe during pregnancy.

If you are worried about taking medicines while you are pregnant, talk to your doctor about the risks for both you and your baby. The risks of not treating your gestational diabetes could be much higher than the risks of taking medicine.

Labour and birth

Usually, gestational diabetes does not seem to impact vaginal birth.

If you have diabetes, it's strongly recommended that you give birth with the support of a consultant-led maternity team in a hospital.

Read more about where you can give birth, including in hospital.

After giving birth

After giving birth, your baby will be monitored for the first 24 to 48 hours. A midwife will check your baby's blood glucose with a heel-prick blood test 2 to 4 hours after birth.

It's a good idea to breastfeed your baby. Feeding your baby as soon as possible after the birth (within 30 minutes) and often (at least every 3 hours) during the next 24 hours can help keep your baby's blood glucose at a safe level. Some people express colostrum during late pregnancy so it will be available if needed to treat low blood glucose levels.

If the heel prick test shows that your baby has low glucose, they may be given a drip to increase their blood glucose. Read more about special care for babies.

Breastfeeding can also help you to bond with your baby.

If you needed to take medicine for gestational diabetes, you will usually be advised to stop taking them straight after the birth. You will be offered a blood test to check your blood glucose levels before you go home and at your 6-week postnatal check.

You should also have regular tests for type 2 diabetes, especially if you are planning another pregnancy. If you are not planning another pregnancy, you should have a test every 3 years.

How can I access subsidised diabetes products and services?

If you have gestational diabetes and are eligible for Medicare, you can register with the National Diabetes Services Scheme (NDSS). This gives you access to subsidised NDSS products and services to help you manage your condition, including:

• blood glucose monitoring strips
• insulin delivery devices
• needles

Supplies are available through NDSS Access Points, which are usually community pharmacies. Find your nearest pharmacy through healthdirect's Service Finder tool.

The National Gestational Diabetes Register can also provide you with:

• information
• advice
• screening reminders

Find out more about the National Diabetes Services Scheme and the services they offer to people with diabetes, including gestational diabetes.

Can gestational diabetes be prevented?

Gestational diabetes often can't be prevented.

You can reduce your risk by maintaining a healthy weight and keeping physically active.

If you are already pregnant and are at a high risk of developing gestational diabetes, speak to your doctor or a dietitian for advice.

Managing gestational diabetes can reduce the chance of having type 2 diabetes after pregnancy. You can:

• maintain a healthy weight
• eat a healthy diet
• be physically active
• have regular screening tests for diabetes, as recommended by your doctor

Complications of gestational diabetes

During pregnancy

High blood sugar levels during pregnancy put you at a higher risk of pregnancy problems including:

• a large baby (over 4.5kg)
• miscarriage or stillbirth
• high blood pressure
• pre-eclampsia
• needing interventions in labour, such as a caesarean birth

After pregnancy

Having gestational diabetes greatly increases your risk of developing type 2 diabetes 10 or more years in the future. Around 1 in 2 people diagnosed with gestational diabetes will develop type 2 diabetes in the future. Your baby is also at greater risk of developing obesity and type 2 diabetes in later life.

Resources and support

Contact your doctor or child health nurse for advice.

If you are diagnosed with gestational diabetes, you can contact the National Diabetes Services Scheme Helpline on 1800 637 700.

For more information on a healthy diet during gestational diabetes, download Diabetes Australia's booklet Gestational Diabetes: Caring for yourself and your baby.

For more information on looking after your health after pregnancy and into the future, download Diabetes Australia's booklet Life after gestational diabetes.

For further information on gestational diabetes, contact Diabetes Australia.

If you are pregnant or breastfeeding and would like to find out more about your medicines call Medicines Line on 1300 633 424 (Monday to Friday, 9am to 5pm AEST).

Speak to a maternal child health nurse

Call Pregnancy, Birth and Baby to speak to a maternal child health nurse on 1800 882 436 or video call. Available 7am to midnight (AET), 7 days a week.