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Gestational diabetes: What is it and how does it affect pregnancy?

You may have heard of friends having gestational diabetes through their pregnancy, or maybe you’ve recently been diagnosed? It’s good to know that despite coming with serious risks, you can manage gestational diabetes with the supervision of your GP and medication if you need to.

Gestational diabetes is a form of diabetes – impaired blood sugar regulation – that happens during pregnancy. Its incidence has tripled over the past couple of decades and currently affects 15% of Australian women. It carries health risks for mother and baby, so it’s important to be aware, get tested and know how to manage it if you’re diagnosed.


Hormonal changes during pregnancy, particularly after 20 weeks of gestation, make your body resistant to insulin. Insulin is an important hormone released by the pancreas that keeps blood sugar levels under control. The bodies of most mums-to-be can adapt by making more insulin, but some women struggle.


If you're 40 or older, overweight, have polycystic ovary syndrome (PCOS) or a family history of type 2 diabetes, you have an increased risk of being diagnosed with gestational diabetes. Some ethnic groups (including Asian, Aboriginal, Indian, Torres Strait Islander, Pacific Islanders, Maori, Middle Eastern and non-white African backgrounds) carry a higher risk of developing gestational diabetes. But it’s important to note that some women who develop gestational diabetes have no known risk factors.


Usually, you may not experience any obvious symptoms, which is why it’s vital for all pregnant women to be tested. If you do experience symptoms, they can include excessive thirst, urination, tiredness and thrush.


Your GP will recommend you be tested for gestational diabetes during pregnancy using an oral glucose tolerance test between 24–28 weeks of pregnancy. Testing can be organised through your GP, obstetrician, midwife or hospital maternity service, depending on your pregnancy plan.

The test involves fasting overnight and then having a blood test followed by a drink containing glucose. Two more tests, one and two hours after the drink, are then conducted to check if your blood sugar level is high.


In the short term, your baby can grow very large, increasing the chances of a problematic delivery, including obstruction and the need for intervention (with forceps or a vacuum device). After they’re born, babies have a greater risk of jaundice, breathing difficulties and struggling to feed, says endocrinologist Alison Nankervis from Royal Melbourne Hospital. They could also have low blood glucose levels.

Diabetes Australia spokesperson Melinda Morrison explains, “This is because the baby is no longer receiving extra glucose from their mother, but they continue to make more insulin than a baby usually would, causing their blood glucose levels to drop.” She says while they won’t be born with diabetes, they do have increased risk of developing it down the track.

In the longer term, the baby has greater risk of becoming overweight, as well as developing raised blood pressure and heart disease.

“There’s still a lot to be learned about that,” says Nankervis. “We not only have the short-term impact on the baby and also the mother, but there’s a potential to have this terrible cycle of increasing risk of diabetes that relates to their in-utero exposure to abnormal glucose levels.”

Around half of mums with gestational diabetes will develop type 2 diabetes or pre-diabetes within 10–20 years, says Morrison.


While being diagnosed with gestational diabetes may come as a shock, the risk of health problems to mum and bub can be reduced if it's well managed.


Managing your gestational diabetes will involve support from a team of health professionals, including a diabetes educator and dietitian and maybe even specialists for more serious cases. But for all women with gestational diabetes – as with any form of diabetes – Nankervis says diet and exercise are the foundation of good management, as well as avoiding excess weight gain.


This means following all the principles of a healthy diet, focusing on the type and quantity of carbohydrates and their even spread throughout the day, as well as cutting out processed foods high in sugar and refined carbohydrates with low nutritional value. Find out more about healthy eating for diabetes management.

A Mediterranean-style diet has been shown to help manage diabetes. The cornerstone of this diet is eating an abundance of plants and whole foods including vegetables, legumes, nuts, seeds, fruit and wholegrains, and using extra virgin olive oil for cooking and salads. Fish and dairy are eaten in moderation, red meat is kept to a minimum and processed foods and sweets are avoided.


Don’t forget to integrate activity into your life that’s safe for pregnancy, like walking or swimming, which will also help control your blood sugar levels, although any new strenuous exercise should be checked with your health professional first. Self-monitoring your blood glucose levels is another vital part of managing gestational diabetes.


It’s worth noting that in some cases, exercise and embracing a healthy diet may not be enough to manage your gestational diabetes and you may need medication. Your GP or health professional will guide you.


Morrison recommends regular checks for type 2 diabetes after the pregnancy, including a follow-up oral glucose tolerance test 6–12 weeks after the baby is born. Ongoing tests are then recommended about once a year, depending on risk for type 2 diabetes.

This is critical for future pregnancies as well, says Nankervis. “Mums who have type 1 or type 2 diabetes when they become pregnant have a greater risk of miscarriage and birth defects, pre-eclampsia, high blood pressure and stillbirth,” she tells.

Above all, it’s recommended that the whole family maintains a lifelong healthy diet and are physically active for mum and bub to be their healthiest.

Sources: Australian Institute of Health and Welfare, Better Health Channel, Diabetes Australia, Diabetes NSW & ACT, Hormone Health Network, National Diabetes Services Scheme, Science Daily, Stanford Children’s Health.

Words by Natalie Parletta
First published March 2020 

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