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What is gestational diabetes?

Gestational diabetes is when you develop high blood sugar (glucose) during pregnancy, which can happen because of hormone changes that occur in your body during this time. 1

It affects women who have not been living with diabetes before pregnancy, and can occur at any stage but is most common during the second or third trimester (six to nine months) of your pregnancy. 2

Gestational diabetes is common and about one in seven pregnant women will develop gestational diabetes.3  It has the potential to lead to complications for you and your baby and therefore it is important that it is identified, so it can be managed appropriately. 4

All pregnant women should be tested for gestational diabetes between 24 to 28 weeks (unless they have been diagnosed with type 1 diabetes or type 2 diabetes before pregnancy). Women who have risk factors for gestational diabetes may be tested earlier in their pregnancy. 1, 3, 5

Symptoms and causes of gestational diabetes

Many women don’t feel symptoms of gestational diabetes, but if you do, they are often difficult to spot as they can easily be confused with normal pregnancy symptoms.2 Some of them may include: 5

  • Feeling thirstier than usual
  • Needing to pass urine more often than usual 
  • Having a dry mouth 
  • Feeling tired 

Diabetes in pregnancy is caused by changes in your hormones during pregnancy. As pregnancy progresses, the placenta produces hormones and this can lead to your body not producing enough of a hormone called insulin, which controls your blood sugar levels. 2, 4

Risk factors for gestational diabetes

While any woman can develop gestational diabetes when they are pregnant, the following factors put you at a greater risk: 4,6

  • Older age
  • Overweight and obesity
  • Gestational diabetes during a previous pregnancy
  • A family history of diabetes
  • Smoking 
  • Ethnicity (if you are of south Asian, Black, African-Caribbean or Middle Eastern origin, you are at greater risk)

Gestational diabetes is defined as having high blood sugar that has started, or is first recognised, during pregnancy. Unlike type 1 and type 2 diabetes, it is often temporary and for many it will be resolved once pregnancy ends.

However, some cases can inevitably uncover undiagnosed pre-existing type 2 diabetes. To find out more about type 2 diabetes, speak to your healthcare professional and you can also read our article here.

Potential effects of gestational diabetes

If you have gestational diabetes, it is good to be aware that this can lead to potential complications for both you and your baby.

For mothers, it can increase your risk of preeclampsia (a pregnancy complication that usually begins after 20 weeks of pregnancy, which is characterised by high blood pressure and signs of damage to another organ system, most often the liver and kidneys), as well as your risk of developing type 2 diabetes and cardiovascular disease after pregnancy. 4, 7

Gestational diabetes can affect your baby too. You may have a larger baby, which in some cases may lead to complications during birth. In the longer term, there is also an increased risk of your child developing type 2 diabetes and obesity at some point in their life. 

However, it is also important to remember that there are things you can do to help reduce your risk of developing diabetes in pregnancy and manage it once identified, which we will discuss in more detail below. 5

Prevention and screening for gestational diabetes

It is not always possible to prevent gestational diabetes – as explained above, some risk factors mean some women are more likely to get it. However, there are things you can do to help reduce your risk. For example, you may be able to control your blood glucose levels during pregnancy by following a healthy diet, managing your weight, staying active through moderate exercise, and monitoring your blood glucose levels regularly. It is important to work with your healthcare professional who will help you manage this and identify together if medication could be right for you. 5

As it can be difficult to diagnose gestational diabetes from its symptoms, your doctor will screen you for it by checking your blood glucose levels using a test known as the oral glucose tolerance test (or OGTT). This will often happen between the 24th and 28th weeks of your pregnancy, or earlier if you have been identified as ‘high risk’. This normally involves the doctor measuring your blood glucose level via a blood test after you have not eaten for a while, and then checking it again sometime after giving you a sugary drink. 5

Identifying diabetes in pregnancy and managing your blood glucose levels during pregnancy can help reduce potential complications, like those mentioned in the section above, for you and your baby.

Treatment of gestational diabetes will depend on your individual needs, and it is important to work with your healthcare professional who will support you to find the right approach for you. If you want more information about your treatment, you can read our article on this topic here.

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  1. Mack LR and Tomich PG. Gestational Diabetes: Diagnosis, Classification, and Clinical Care. Obstet Gynecol Clin North Am. 2017; 44:207–217.
  2. NHS. Gestational diabetes. Available from: https://www.nhs.uk/conditions/gestational-diabetes/ Last accessed: January 2024.
  3. National Diabetes Services Scheme (NDSS). (n.d.). Understanding gestational diabetes. Available at: https://www.ndss.com.au/about-diabetes/gestational-diabetes/understanding/ Last accessed: January 2024.
  4. Zhu Y and Zhang C. Prevalence of Gestational Diabetes and Risk of Progression to Type 2 Diabetes: a Global Perspective. Curr Diab Rep. 2016;16:7.
  5. International Diabetes Federation. IDF Atlas 10th Edition, 2021. Available from: https://diabetesatlas.org/idfawp/resource-files/2021/07/IDF_Atlas_10th_Edition_2021.pdf Last accessed: January 2024.
  6. Zhang C, Rawal S and Chong YS. Risk factors for gestational diabetes: is prevention possible? Diabetologia. 2016; 59:1385–1390.
  7. Mayo Clinic. Preeclampsia. Available at: https://www.mayoclinic.org/diseases-conditions/preeclampsia/symptoms-causes/syc-20355745 Last accessed: January 2024.