Gestational diabetes

In Australia, more than 1 in 6 women are affected by gestational diabetes.

What is Gestational diabetes mellitus (GDM)

Gestational diabetes mellitus (GDM) is a type of diabetes that only develops during pregnancy. Hormones from the placenta block the usual way the body processes sugar, causing high blood sugar levels. Both mother and baby can be affected by GDM through pregnancy and in the long term.

For most mothers with GDM blood sugar levels will return to normal after giving birth. For some mothers blood sugars levels will stay high and may lead to the development in GDM in future pregnancies.

Diagnosis and management of GDM are important to reduce the risk of pregnancy and post-birth complications. Good management of GDM throughout pregnancy can help keep your baby healthy and prevent a difficult birth. 

Diagnosing Gestational diabetes mellitus

Generally, there aren't any physical signs to indicate the development of gestational diabetes. Some symptoms may be increased thirst and more frequent urination.  

An oral glucose tolerance test (OGTT) will be done at around 24-28 weeks of pregnancy to test for GDM. The test may be done earlier in pregnancy if an individual has risk factors, such as:

  • a family history where direct members had type 2 diabetes mellitus (T2DM)
  • being over the age of 40 years
  • having had GDM in a previous pregnancy
  • previously had high blood sugar levels
  • being a First Nation woman
  • needing to take some anti-psychotic or steroid medication
  • living with Polycystic ovary syndrome (PCOS)
  • being above a healthy weight range
  • previously given birth to a large baby (above 4.5 kgs)
  • being of African, Polynesian, South Asian, Chinese, Southeast Asian, Middle Eastern, Hispanic and South American background.

Gestational diabetes can still affect an individual even if they don't have any risk factors.

See Tests and scans during pregnancy for more information.

Gestational diabetes mellitus and your baby

Developing gestational diabetes mellitus during pregnancy does not mean that a mother can't have a healthy pregnancy, delivery, or baby. Having GDM won't lead to a baby being born with diabetes, however, there is a higher risk that they may develop type 2 diabetes later in life.

Management through pregnancy

Managing GDM well can have a positive impact on pregnancy, delivery, and the health of the baby.

Some key actions to consider to reduce short-term complications for the baby include:

  • monitoring and regularly checking blood sugar levels
  • seeing a dietitian for possible diet changes and nutrition counseling
  • regular, moderate exercise, unless your doctor has advised not to
  • use of medication or insulin, where prescribed by a doctor.

Potential complications

When GDM is managed well, it can: 

  • reduce the risk of complications like miscarriage, stillbirth, and premature birth
  • lower the likelihood of birth interventions like induction 
  • lower the likelihood of emergency caesarean sections  
  • lower the risk of complications that can mean special or intensive care for your baby. 

If a mother had consistently high sugar levels then the baby's body will produce more hormones to keep these blood sugar levels done. Post-birth, the baby may be getting less sugar from the mother's blood but could still be producing high levels of hormones to control it.  This can make the baby's blood sugar levels too low.

Heel prick test will be done regularly after birth to check the baby's blood sugar levels are too low. Additional feeds or a supplement of glucose may be recommended by your doctor to help increase blood sugar levels to normal levels.


Being healthy and active can help reduce the risk of a child developing type 2 diabetes in the future. 

See Healthy eating for children and Physical activity for ways to keep children healthy and reduce their risk of chronic health conditions in the future.


Mothers who had GDM  can still breastfeed their baby, however, it may be slightly more challenging. Excess sugar levels in a mothers blood may flow over into breastmilk, which can be passed to the baby. It is important to have good control over blood sugar levels when breastfeeding.

Your doctor or midwife may recommend expressing colostrum before birth to help give extra nutrients and stabilise your baby's blood sugar levels. 

An International Board-Certified Lactation Consultant (IBCLC) can offer information and support for breastfeeding after having GDM.

Last updated Monday 19th February 2024