Skip to main content

Gestational Diabetes

What is it?

Gestational diabetes mellitus (GDM) is diagnosed in an estimated 12% – 14 % of pregnancies. It occurs when the body is unable to keep blood glucose levels within normal ranges.


A quick lesson in carbohydrate metabolism to get you up to speed with what this actually means:

Through the process of digestion, carbohydrates found in foods we consume (think milk, legumes, breads, rice, veg, fruit to ice cream, lollies, pastries, pizza) are broken down into a smaller, more usable form of currency called glucose. When glucose hits the bloodstream, the pancreas secretes a hormone called insulin. Its job is more or less to chaperone the glucose into neighbouring cells. It does so by ‘unlocking’ the cell to allow glucose in. This allows cells to use glucose for energy.


In the case of GDM, hormones produced by the placenta disrupt the action of insulin, causing a backlog of glucose in the bloodstream. This occurs for one of two reasons. Either there is not enough insulin being secreted by the pancreas to clear the chaperone the glucose into cells, or the cells that take up the glucose aren’t unlocking in response to insulin.


What are the risks of GDM?

Untreated GDM can lead to complications during pregnancy, including early delivery, distress for the baby during birth, large baby, and low blood glucose in baby at birth.


The good news is that GDM generally resolves after giving birth when a woman’s hormones return to normal.


Am I likely to get it and how will I know?

The risk of developing GDM is increased with:

  • Age at conception
  • If you had GDM during a previous pregnancy
  • A family history of type 2 diabetes or first degree relative who has had GDM
  • PCOS
  • Rapid weight gain during first half of pregnancy
  • Being above a healthy a weight at time of conception
  • Melanesian, Polynesian, Indian subcontinent, Middle Eastern or Asian background


Most women will not have symptoms with GDM and may be surprised to discover they have it at all.  All pregnant women will have an oral glucose tolerance test (OGTT) between 24 and 28 weeks gestation. This involves drinking a solution of glucose equivalent to 12 tsp of sugar, the same amount you would find in 700ml coke! Your blood glucose levels will be measured before the test (fasting) and at various time intervals after drinking the glucose solution. GDM is confirmed if your blood glucose levels remain above the normal range at any of these testing intervals.


How can I manage it?

The good news is it is possible to keep your blood glucose levels within a normal range throughout pregnancy and have a perfectly safe birth and healthy bub. This requires regular monitoring of blood glucose levels and modifications to diet and lifestyle. In some women, diabetes medications, or insulin may be needed to keep blood glucose levels within target ranges. Where diagnosis is confirmed, your GP or care provider will link you in with a diabetes educator and dietitian to help you make these changes.


What dietary changes and I going to have to make?

Generally speaking – the type and amount of carbohydrate containing foods consumed will need to be modified to keep your blood glucose levels within your target range. This will be individualised to you.

And no, this doesn’t mean you have to give up chocolate or ice cream entirely, your dietitian will teach you how to include these foods in a healthy way.


Some general health eating and lifestyle tips for managing GDM

  • Swap refined sources of grains/cereals e.g. white rice, rice cakes, many breakfast cereals, pizza, pastries, muffins, for whole grain alternatives such as brown rice, quinoa, oats, grainy/seedy crackers, grainy breads.
  • Base ½ your meal on low carbohydrate veg/salad (e.g cauli, broccoli, zucchini, capsicum, carrot, mixed leaves beetroot)
  • Get to know your food labels to avoid sneaky added sugars. A good rule of thumb is to look for products that contain < 10g sugar per 100g
  • 100% real fruit juices may seem ‘healthy’ but they often contain upwards of 5 tsp sugar per glass. Go for a veggie-based juice instead.
  • Exercise improves the action of insulin, so aim to move for 30-45 minutes a day at a pace that is safe and comfortable for you. This can be split up throughout the day.


Written by Hannah Wilson, Dietitian