Gestational diabetes

What is gestational diabetes?

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

If you have gestational diabetes, your pregnancy hormones reduce your body’s ability to use sugar (glucose) properly. This leads to higher-than-normal levels of sugar in your blood, which can be unhealthy for both you and your baby.

Around 1 in 10 to 1 in 20 pregnancies are affected by gestational diabetes. Gestational diabetes is usually diagnosed between the 24th and the 28th week of pregnancy, after a routine screening test.

What are the symptoms of gestational diabetes?

Typically, gestational diabetes doesn’t cause any symptoms, and is diagnosed with routine antenatal screening.

What causes gestational diabetes?

When you are pregnant, your placenta produces hormones to help your baby grow. These hormones also block the action of insulin in your body. This is known as insulin resistance. In a normal pregnancy, your body will make 2 to 3 times more insulin if you are pregnant. 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, or gain too much weight in the first half of your pregnancy
• are over 35 years old
• have a family history of type 2 diabetes
• come from certain ethnic backgrounds including Aboriginal and/or Torres Strait Islander
• were diagnosed with gestational diabetes in a previous pregnancy, or had a large baby in a previous pregnancy
• have polycystic ovary syndrome
• are taking some types of antipsychotic or steroid medicines

How is gestational diabetes diagnosed?

Screening for gestational diabetes is recommended in all pregnancies. Most people are tested between 24 to 28 weeks of pregnancy. If you are at higher risk, your doctor may recommend that you test earlier.

The test used in Australia to screen for gestational diabetes is called the oral glucose tolerance test (OGTT). You need to fast for 10 hours (usually overnight, missing breakfast). You will have a blood test to check your baseline blood sugar level. Then you will be given a drink that contains 75g of glucose. Further blood tests are then performed after 1 and after 2 hours. You will be usually need to stay at the laboratory for the full duration of the test.

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

How is gestational diabetes managed?

If your doctor diagnoses gestational diabetes, it’s important to follow their health advice.

Managing the condition and keeping your blood glucose levels under control helps reduce the chance of complications for both you and your baby.

• You may need to learn to monitor your blood sugar levels at home
• Your doctor may refer you to an obstetrician, dietitian and/or diabetes nurse educator
• You may need more frequent antenatal appointments

Blood glucose monitoring

You will usually need to check and record your blood glucose several times a day. The most common times are straight after waking up, and either 1 or 2 hours after each main meal.

Your medical team will teach you how to check your blood glucose at home with a blood glucose meter (glucometer) and 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.

If you are eligible for Medicare, you may be eligible to access subsidised diabetes products, including blood glucose test strips, through the National Diabetes Services Scheme.

A healthy diet

• Following a healthy eating plan is important in managing gestational diabetes.
• 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.
• 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 that raises your breathing or heart rate, such as walking daily, can help you manage your blood glucose levels.
• Always check with your doctor first before you start exercising while you are pregnant.

Medicine

• You may need medicine to lower your blood sugar levels, if they continue to remain high even after changing your diet and increasing your levels of physical activity.
• Insulin injections and metformin pills are both considered safe to take during pregnancy.
• Your doctor will discuss the most appropriate treatment for you.
• If you need to use insulin, you may be referred to a diabetes nurse educator who will teach you how to safely inject insulin.
• If you already have diabetes when you become pregnant, discuss with your doctor whether you will need to change any of your medicines.
• If you are worried about taking medicines while you are pregnant, discuss the risks with your doctor. Remember, the risks of not treating your gestational diabetes could be much higher than the risk associated with the medicine, for both you and your baby.

Labour and birth

• Most people with gestational diabetes can have a 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 the birth

• Your baby will need special monitoring for the first 24 to 48 hours after birth. A midwife will check your baby’s blood glucose with a heel-prick blood test a blood glucose test 2 to 4 hours after birth.
• 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 colostrum will be available if needed to treat mild to moderate low blood glucose levels.
• If your baby’s blood glucose can’t be kept at a safe level, they may need extra feeds with expressed colostrum, expressed breastmilk, formula or glucose. In some cases, your baby may be given a drip to increase their blood glucose. Read more about special care for babies.
• 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 every year if you are planning another pregnancy or if you’re not feeling well. If you are not planning another pregnancy, you should have a test every 3 years.
• If you have had gestational diabetes, it’s a good idea to breastfeed your baby. As well as providing an opportunity for bonding between you and your baby, it reduces your future risk of developing type 2 diabetes.

How can I access subsidised diabetes products and services?

If your doctor has diagnosed you with 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

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.

If you had gestational diabetes in a previous pregnancy, you’re at higher risk of developing it again. Your doctor may recommend screening for gestational diabetes earlier in the pregnancy (at around 12 to 16 weeks), and then again at around 26 weeks of pregnancy.

What are the 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

Your baby will not usually be born with diabetes.

After pregnancy

Having gestational diabetes greatly increases your risk of developing type 2 diabetes in the next 10 to 20 years. 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.

To reduce your risk of developing type 2 diabetes:

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