What is gestational diabetes?
Gestational diabetes is a type of diabetes that starts during pregnancy. If you have gestational diabetes, your body can’t use sugar (glucose) properly. This leads to higher than normal levels of sugar in the blood, which can be unhealthy for both you and the baby.
As gestational diabetes is a condition that occurs during pregnancy, it is not the same as having pre-existing diabetes during your pregnancy.
1 in every 8 women in Australia develops gestational diabetes, usually around week 24 to week 28 of pregnancy, although it can happen earlier.
What are the symptoms of gestational diabetes?
Typically, women with gestational diabetes have no symptoms. Most women are diagnosed after routine tests during pregnancy.
What causes gestational diabetes?
When you are pregnant, your placenta produces hormones to help the baby grow. These hormones also block the action of insulin in your body (called insulin resistance). Women need 2 to 3 times more insulin when they are pregnant.
If you already have insulin resistance, your body may not be able to cope with this extra demand for insulin. That will lead to blood glucose levels being too high.
You are at higher risk of developing gestational diabetes if you:
- are above the healthy weight range or gaining too much weight in the first half of pregnancy
- are over the age of 35 years
- have a family history of type 2 diabetes
- come from an Aboriginal and Torres Strait Islander or some Asian backgrounds
- have had gestational diabetes before
- have had polycystic ovary syndrome
- have had a large baby before
- are taking some types of anti-psychotic or steroid medications
How is gestational diabetes diagnosed?
All women are tested for gestational diabetes, usually at 24 to 28 weeks of pregnancy. If you are at higher risk, you may be tested earlier.
The test for gestational diabetes is called an ‘oral glucose tolerance test’ (OGTT). You need to fast for 10 hours (generally overnight, missing breakfast). A blood test is taken, followed by a 75g glucose drink and further blood tests at 1 and 2 hours later. You will be required to remain at the laboratory for the 2-hour test.
How is gestational diabetes managed?
If you are diagnosed with gestational diabetes, it’s important to follow your doctor’s advice. Managing the condition and keeping your blood glucose levels under control helps avoid complications for both you and your baby.
You may be referred to an obstetrician and dietitian and may need more frequent antenatal appointments and regular monitoring of your blood sugar levels.
Monitoring your blood glucose levels
Your medical team will give you a target range for your blood glucose levels. You will need to check these at home while you are pregnant.
You can purchase a blood glucose measuring kit from your local pharmacy or diabetes centre, or from Diabetes Australia in your state or territory — call 1800 637 700 for help.
To test your blood glucose levels, you prick your finger with a lancet and put a small drop of blood onto a testing strip. Then you insert the strip into a meter, which reads your blood glucose level.
A healthy diet
Following a healthy eating plan is important in managing gestational diabetes. Eat small amounts often and try not to put on too much weight. A healthy diet for women with gestational diabetes includes:
- a carbohydrate with every meal and snack (spread your carbohydrate intake over 3 small meals and 2 to 3 snacks each day)
- a variety of foods that contain the nutrients you need during pregnancy
- high-fibre foods
- avoiding foods and drinks that contain a lot of sugar
- limiting fat, especially saturated fats
For more information on a healthy diet during gestational diabetes, download Diabetes Australia’s booklet Gestational Diabetes: Caring for yourself and your baby.
Moderate intensity physical activity — physical activity that raises your breathing or heart rate — can help you manage your blood glucose levels and reduces insulin resistance.
The best form of exercise if you have gestational diabetes is to build walking into your daily routine. Always check with your doctor first before you start exercising while you are pregnant.
If your blood sugar levels remain high despite changes to your diet and an exercise regime, you may need medication to lower your blood sugar levels.
Both insulin injections and metformin pills have been shown to be safe for the unborn baby. 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 for both you and your baby.
Labour and 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 after the birth since their blood glucose levels may be too low for a while. To check, they will have a heel prick blood test 2 to 4 hours after the birth. Feed your baby as soon as possible after the birth (within 30 minutes) to help keep your baby's blood glucose at a safe level.
If your baby's blood glucose can't be kept at a safe level, they may need extra care. Your baby may be given a drip to increase their blood glucose.
Read more about special care for babies.
If you had gestational diabetes, you can stop all treatment after the birth. You should be offered a test to check your blood glucose levels before you go home and at your 6-week postnatal check. You should also be given advice on diet and exercise.
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.
Can gestational diabetes be prevented?
Gestational diabetes often can’t be prevented. But you can reduce your risk by being a healthy weight. If you are overweight before you fall pregnant, it is a good idea to try to lose some weight first.
If you are already pregnant and you are overweight, don’t try to lose weight now. But it’s important to keep your weight gain within a healthy range. Your doctor can help you with this. Avoiding too much weight gain in the first two trimesters is a great way of preventing gestational diabetes.
If you have had gestational diabetes in a previous pregnancy, you’re at higher risk of developing it again. Your doctor may do an oral glucose tolerance test at around 12 to 16 weeks to check your blood glucose levels, and then again at around 26 weeks.
What are the complications of gestational diabetes?
If your blood sugar levels remain high during your pregnancy, this may lead to pregnancy problems such as a large baby, miscarriage or stillbirth. Having a large baby can lead to complications and injury during the birth, and increase the chances of having intervention in labour such as a caesarean birth. But the baby will not be born with diabetes.
If you have gestational diabetes, you are at higher risk of developing high blood pressure while you are pregnant and a 50% increased risk of developing type 2 diabetes in the future. Your baby is also at greater risk of developing type 2 diabetes in later life.
To reduce your risk of developing type 2 diabetes:
- keep to a healthy weight
- eat a healthy diet
- be physically active
- check your blood glucose levels
You can also call Pregnancy, Birth and Baby on 1800 882 436 to speak to a maternal child health nurse for advice and support.
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Last reviewed: October 2021