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Gestational Diabetes (GDM)

Gestational diabetes in pregnancy explained by Dr Adeline Chan, obstetrician in Sydney

In Australia, 1 out of 7 pregnant women is affected by gestational diabetes (GDM). The good news is, more than half of these women would be able to manage their GDM without medications.

Traditionally, screening for GDM happens between 26-28 weeks. However, over the last 5-8 years or so, there has been a shift to offer early screening for patients with high risk for GDM, which usually occurs before 16 weeks of pregnancy. The risk factors include :

· History of GDM

· Strong family history of DM or GDM

· Women >40 years old

· Previous baby >4.5kg

· History of PCOS

· Patients of certain ethnicity

Once GDM is diagnosed, women would be offered a review with a dietician and diabetes educator. These sessions would educate pregnant mothers on how to check their sugar levels and dietary modifications. You would also need to see an endocrinologist “diabetes doctor”.

You may also need to have growth ultrasounds in your pregnancy to monitor your baby’s growth.

There are some risks associated with GDM and they may include an increased risk for operative delivery (ie. assisted vaginal or caesarean section), increased blood loss, big baby, shoulder dystocia, admission to nursery, stillbirth and others.

Generally, the average BSL targets for pregnancy is <5.2 for fasting levels, and <6.8 for 2 hours post meal. Meal servings should include 2-3 serves of carbohydrates for mains, and 1-2 serves for snacks. It is important to note that actual carbohydrate content of the meals, rather than just cutting out the “sugar” in the meal. 1 serve of carbohydrate is 15g. You can usually find this information on the food packaging.

Sometimes despite strict diet control, you may still need to be on some medications and this is by no means a fault of yours. As the pregnancy progresses, the placental hormones increase insulin resistance. Medications that are used in pregnancy are well studied and you should not worry about its safety in pregnancy. It is important to keep your BSLs stable rather than fluctuating throughout the day.

And finally, after having the baby you will have your BSLs checked several times while in hospital. It usually returns back to normal almost immediately! If it doesn’t, then there is a possibility that you have had diabetes before the pregnancy. Also, 50% of mothers with GDM history develops Type 2 Diabetes in the future so, remember to do a formal sugar test (the 2- hour GTT) at 6-8 weeks post the birth of your baby and regularly every few years.

Dr Adeline Chan is a specialist obstetrician and gynaecologist in Sydney, serving the Western Sydney and Hills District area.

Feel free to leave us a message at or call our friendly staff at 02 9629 3559 if you have any questions or would like to make an appointment.


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