What to eat before and after the gestational diabetes test

Pregnancy woman with young boy kissing her pregnant belly and looking at the camera

What is gestational diabetes?

Gestational Diabetes Mellitus or GDM is a type of diabetes that occurs during pregnancy. It is diagnosed using a 2-hour Oral Glucose Tolerance Test (OGTT) at around 26 to 28 weeks of pregnancy*.

The OGTT is a blood test ordered by your GP, obstetrician, or antenatal clinic. This is a ‘universal test’, which means all pregnant women should have this test.

How do I prepare for my OGTT?

Discuss any medication, both prescription and non-prescription, with your doctor or midwife. You may need to stop medications before the test. The OGTT is a fasting test, so have nothing to eat from 9pm the night before the test. Water is permitted in small amounts. You will need to avoid strenuous exercise and smoking for 8 hours before the test. During the test you will need to sit for the two hours. Even walking around the shops can interfere with the test results.

Does my diet affect the outcome of the test?

Some written information provided to women can be a little misleading or hard to understand.

Some examples of (confusing) advice we have seen include…

Continue to eat your normal balanced diet making sure you include at least 150 grams per day of carbohydrate for at least 3 days prior to the test. You diet should include cereals, grains, rice,  pasta, fruits, crackers and starchy vegetables such as potatoes, beans and corn


 “..consume at least 10 serves of carbohydrate each day”

We get lots of questions from concerned women that “this seems to recommend a lot of carbohydrate!”. Many ask,

Is this ON TOP of what I usually eat?


What happens if I don’t eat this?

To make sense of this it helps to know how much carbohydrate is in food and how much most Australians eat.

First of all, the ‘minimum of 150g per day’ is easily consumed by most people. Serves of carbohydrate can be quantified in 15g serves and usually equates to a ‘serve’ of food. For example, a slice of bread, half a cup of pasta, a glass of milk, a tub of yoghurt, a medium potato, or an apple, orange or banana each contain about 15g of carbohydrate.

So, by having cereal and milk or toast for breakfast, a sandwich, bread roll or wrap at lunch, and meat with vegies (including a potato, sweet potato, or corn) or a stir fry with some noodles or rice at dinner, plus snacks through the day of fruit and yoghurt, or even plain biscuits, you will easily consume the minimum 150g of carbohydrate per day required.

Some studies have shown that not eating ENOUGH carbohydrate before your test might give a ‘false positive’ result – it might look like you have GDM when you do not (eek!).

To ensure you get the correct result following your OGTT we advise women to continue to eat a healthy balanced diet that includes foods from all the food groups in the days leading up to their test. Use the above examples as a guide to what you might eat throughout the day.

What happens after an OGTT?

If your results are normal you can continue with your usual antenatal care. If your blood glucose levels are raised you have GDM.  It is best practice for you to see an range of specialists including an endocrinologist, diabetes educator and a maternal health specialist dietitian to assist you in the management of GDM.

What changes do I need to make?

A healthy lifestyle incorporating diet and exercise is the starting point to best manage GDM.  Regular meals incorporating slow acting carbohydrates, reducing saturated fats and added sugars/ultra-processed foods and including regular walks and other physical activity will help manage GDM.

A dietitian is the best person to help you build your knowledge, skills and confidence to make these and many more changes to optimise your health with GDM.

Current research shows us that women with GDM who attend regular appointments with a dietitian during their pregnancy have a greater chance of managing their GDM and weight gain. This in turn helps baby to have good outcomes and reduces your risk of developing diabetes in the future.

So, how often should I see the dietitian?

All studies point to the benefits of ongoing contact and support from an expert maternal health dietitian when managing your GDM. Studies testing the effectiveness of GDM nutrition guidelines have shown improved pregnancy outcomes (less need for insulin and better control of blood glucose levels) when women saw a specialist maternal health/GDM dietitian a minimum of three times during their pregnancy + a postnatal review.

Our Director and Principal Dietitian, Dr Shelley Wilkinson, has applied these findings in health services she has worked in and collaborated with and now brings them to Lifestyle Maternity.

Our specialist maternal health-GDM dietitians are able to tailor a program to support you to adapt guideline recommendations to your lifestyle and preferences. If you need support, please make an appointment to help you achieve your goals. At these appointments a dietitian can assist you to adjust your individual meal plan timing and the content of your diet to optimise your BGLs.

Practical suggestions to help you balance your dietary goals for GDM, manage your weight gain to your individual needs, and develop the healthiest baby possible will be negotiated and matched to your needs.

What does the Lifestyle Maternity GDM service offer?

We would love you to learn to manage your blood glucose levels while still meeting your pregnancy nutrition needs through participating in our innovative gestational diabetes mellitus (GDM) model of care.

 Once you book your GDM package with Lifestyle Maternity you will be sent:

  1. a one-page sheet that summarises your NEED-TO-KNOW dietary modifications. This will help you get your head around and changes you may need to make,
  2. an introductory video to support your first week after diagnosis. It’s a GDM explainer plus more in depth dietary information,
  3. a diary to start keeping a WEEK LONG food and blood glucose record. This will allow your Lifestyle Maternity dietitian to review your progress BEFORE your SECOND appointment with us.

Your individual consult will involve a thorough assessment of your dietary and lifestyle patterns with a personalised action plan being developed in collaboration with the dietitian. This will involve tailoring best practice nutrition guidelines to your personal circumstances and preferences to optimise your health once bub arrives.

The cost of the GDM package (your individual assessment and plan PLUS being sent the starter information sheet, PLUS video link and food and blood glucose diary paperwork, PLUS the review and assessment of this diary by an expert maternity dietitian) is $185. Current Lifestyle Maternity clients will received reduced rates for this appointment ($140).

Each subsequent “review” appointment costs $105. This includes out-of-appointment review of your BGLs and diary prior to each appointment. At your third appointment (your second ‘review’) you will receive a PeNut + Lifestyle Maternity GDM Cookbook (RRP $49). This will help give you extra meal time inspo and includes 30 dietitian-designed, low GI recipes (10 breakfasts, 10 lunch/dinners, and 10 snacks).


Don’t have GDM but still need general nutrition help?

We offer individual consultations and self-paced online courses as we know you all have different learning styles and budgets. Attending an individual session OR online course with a Lifestyle Maternity dietitian will allow you to assess your diet against recommended guidelines and identify changes that can be tailored to your lifestyle and dietary preferences.

In our self-paced online course you will be encouraged and guided to assess your own health habits against pregnancy recommendations, participate in activities around setting health goals for optimal nutrition and learn how to adapt your routines with confidence to achieve these goals to make them stick. More information here.

An individual consult involves a more thorough assessment of your dietary and lifestyle patterns with a personalised action plan being developed in collaboration with the dietitian. If you would like further information book an appointment  now.

* People from the groups below are those who would be considered at higher risk of GDM and should be tested for GDM in EARLY PREGNANCY.

  • Previous hyperglycaemia in pregnancy
  • Previously elevated blood glucose level
  • Maternal age ≥40 years
  • Ethnicity: Asian, Indian subcontinent, Aboriginal and Torres Strait Islander, Pacific Islander, Maori, Middle Eastern, non-white African
  • Family history of diabetes mellitus (first degree relative with diabetes or a sister with gestational diabetes mellitus)
  • Pre-pregnancy body mass index >30 kg/m2
  • Previous macrosomia (baby with birth weight >4500 g or >90th centile)
  • Polycystic ovary syndrome
  • Medications: corticosteroids, antipsychotics

IMAGE CREDIT: Richard Jaimes/Unsplash

IMAGE DESCRIPTION: Pregnancy woman with young boy kissing her pregnant belly and looking at the camera