What is Gestational Diabetes?
Gestational diabetes mellitus is a type of diabetes you can have when pregnant. It is often called GDM for short.
Gestational diabetes will normally be diagnosed with a blood test and an oral glucose tolerance test (OGTT) when you are between 24 and 28 weeks pregnant. You will have a blood test before the glucose drink and then two more blood tests after the drink. Your doctor may get you to do this test earlier in your pregnancy if you have symptoms or risk factors for gestational diabetes.
If you’re diagnosed with gestational diabetes don’t panic. You haven’t done anything wrong and you are not alone.
About one in every seven Australian women have gestational diabetes during pregnancy. It can generally be managed with diet and exercise, although some women may need to take tablets or insulin injections too.
Gestational diabetes usually goes away after the baby is born. Having GDM increases your risk of developing type 2 diabetes later in life.
Why does gestational diabetes happen?
When you are pregnant, the placenta produces special pregnancy hormones. These hormones can make the insulin in your body work less effectively than it normally does which causes high blood glucose levels. If you have a lot of glucose in your blood, it can pass through the placenta to your baby and make them grow too big. This is known as macrosomia.
As well as this, your body might not be able to make enough insulin to meet the extra amount that you need in pregnancy.
What are the risk factors for gestational diabetes?
Factors that may increase your risk of developing GDM during pregnancy include:
- Ethnicity: Asian, Indian subcontinent, Aboriginal, Torres Strait Islander, Pacific Islander, Maori, Middle Eastern, non-white African Diabetes in Pregnancy Multicultural Resources
- Pre-pregnancy body mass index (BMI) >30 kg/m²
- Previous hyperglycaemia in pregnancy
- Previous elevated blood glucose level
- Maternal age ≥40 years
- Family history of diabetes (close relatives with diabetes or a sister with hyperglycaemia in pregnancy)
- Previous macrosomia (baby with birth weight >4500g or >90th percentile)
- Polycystic ovary syndrome
- Medications: corticosteroids, antipsychotics
How is gestational diabetes diagnosed?
Gestational diabetes is diagnosed with a blood test and an oral glucose tolerance test (OGTT). The test requires you to fast for 8-10 hours (generally overnight, missing breakfast). Once you arrive at the clinic you will be given a blood test, followed by a sweet drink containing glucose. An hour later your blood is tested again. You are not allowed to have anything to eat or drink, except water, during this time. A third and final blood test an hour after the second test. The test is looking to see how well your body has used glucose over that period of time.
Some clinics give you the results later that day, but others may take up to 48 hours.
When will I be tested?
All women are tested for gestational diabetes in the 24th to 28th week of pregnancy. This is because symptoms are not obvious. If you are you are classed as being at higher risk you may have the test earlier.
If you have been diagnosed
If you are diagnosed with gestational diabetes there are things you need to do to manage it. A healthy diet, regular exercise, checking your blood glucose levels and taking tablets or insulin all help to manage gestational diabetes by keeping your blood glucose levels in a healthy range. This will reduce the risks to you and the baby.
If you have GDM read more about healthy eating, food swaps and safe exercise for gestational diabetes.
Maintaining a healthy weight
If you are overweight, it is a good idea to try to lose some weight before falling pregnant. This will greatly reduce your risk of being diagnosed with gestational diabetes. You can do this through making changes to the foods you eat, and by doing more physical activity.
If you have fallen pregnant already and you are overweight that’s okay. Don’t try and lose weight during pregnancy. This isn’t good for you or your baby. It is important though to try and keep your pregnancy weight gain within a healthy range. Your GP can help you work out how much weight gain during pregnancy is best for you.
Avoiding too much extra weight gain, especially in the first two trimesters will greatly reduce your risk of being diagnosed with gestational diabetes.
For tailored advice on healthy eating in pregnancy you may find it useful to speak to a dietitian. You can search for a local dietitian here or give our helpline a call for more information on preventing gestational diabetes.
Gestational diabetes a second time
If you do get diagnosed for a second time it can be very upsetting. Gestational diabetes is an extra thing to carry on top of chasing around after your first born, coping with work and whatever else life throws at you.
Try to stay positive – on the plus side you have experience. You already know how to manage the testing, and potentially what foods to avoid to keep your blood glucose levels in target. You may also get extra scans to check on your bub – which is one silver lining!
Don’t panic. Keep the risks in perspective
While there are risks associated with gestational diabetes it is important to remember that every pregnancy has risks, regardless of whether the mother has gestational diabetes. Of course, you want a perfect pregnancy and it’s natural to be worried. Look at your diagnosis as the first step towards reducing any chances of complications. Your healthcare team will be able to guide and support you throughout the rest of your pregnancy to significantly lessen any risks. Read Crystal’s personal story and experience with gestational diabetes.
Will gestational diabetes harm the baby?
Untreated gestational diabetes can cause problems for you and your baby. Women with gestational diabetes are more likely to have a caesarean section, pre-term labour and birth, and induced labour than women without gestational diabetes.
Treating gestational diabetes by keeping blood sugar levels as close to the targets recommended by your GP and healthcare team will reduce the risk of any complications. They will also keep a close eye on your baby and how it grows to prevent any complications from happening.
Can gestational diabetes be prevented?
Unfortunately, gestational diabetes can’t always be avoided. Even if you are a healthy weight, run marathons and steer clear of all processed foods you could still end up being diagnosed with gestational diabetes.
The main things that increase your risk of developing gestational diabetes are:
- A family history of type 2 diabetes
- Certain ethnic backgrounds, including Aboriginal or Torres Strait Islander, Indian, Vietnamese, Chinese, Middle Eastern or Polynesian
- Having gestational diabetes in previous pregnancies
- Being above the healthy weight range
- Have Polycystic Ovary Syndrome
- Being over 35
- Unexplained stillbirth or neonatal deaths or having previously given birth to a very large baby
- Some types of anti-psychotic or steroid medications
Most of these things can’t be changed. However, it’s good to know which ones affect you so that you can focus on the things that are in your control. If you’re planning a pregnancy, it’s a good idea to chat with your GP about your risk of gestational diabetes. They can guide you with how to prevent it in your individual situation.
I’ve had gestational diabetes before? Will I get it again?
If you had gestational diabetes in an earlier pregnancy, studies suggest you are 30-60% more likely to be diagnosed in a future pregnancy. It is a good idea to see your GP to be checked for type 2 diabetes before becoming pregnant a second time.
When you do fall pregnant again, your GP might ask you to start monitoring your blood glucose levels even before you have had the oral glucose tolerance test (OGTT). The OGTT is where you drink the sugary drink and have a blood test. It is not uncommon for your GP to offer you an early OGTT test at around 12-16 weeks, and then again at around 26 weeks.
Not everyone who experiences gestational diabetes in their first pregnancy will get a diagnosis the second time around. You might enjoy this post from Zoe Foster Blake who had gestational diabetes and pregnancy-induced osteitis pubis in her first pregnancy – but not her second.