Gestational diabetes (GDM) is a condition when there is higher than normal blood glucose levels which first occur in pregnancy in a pregnant woman who is not usually affected by Type 1 or Type 2 diabetes.


Gestational diabetes is thought to be due to higher-than-normal levels of a hormone called Human Placental Lactogen (HPL) from the placenta which in turn causes higher blood glucose levels. The vast majority of GDM occurs between 24 and 28 weeks of pregnancy but can occur earlier.

Women who are at higher risk for developing GDM include:

  • Women who have a family history of Type 2 Diabetes
  • Women who are overweight.
  • Women who have an Aboriginal or Torres Strait Islander background.
  • Women who have a South East Asian, Middle Eastern, Melanesian, or Polynesian background.
  • Women who have had GDM in previous pregnancies.


GDM is diagnosed by a test called a Glucose Tolerance Test. This is performed routinely at 26 weeks of pregnancy, but can be performed earlier in women high risk for GDM (see risk factors above).

Being diagnosed with GDM during a pregnancy can be quite upsetting, however it is important to remember that most women diagnosed with GDM will have a healthy pregnancy, a normal vaginal delivery, and a healthy, happy baby with the correct management.


The mainstay of treatment of GDM is healthy eating, regular exercise, and close monitoring of blood glucose levels with the goal of maintaining a normal blood glucose level.

Management will mainly involve the obstetrician and practice midwife. Advice from a dietician, diabetic educator and a medical specialist may occasionally be required.

A tablet named Metformin, or injectable insulin can sometimes be required for control of blood glucose levels should diet and exercise alone not be enough to control blood glucose levels adequately.

If medication is required to manage the blood glucose levels (Metformin or Insulin), induction of labour or Caesarean section will generally be required around the 38-week mark of pregnancy in the interests of safe delivery of the baby.

For GDM controlled with diet and exercise only, the pregnancy can usually be safely taken up to 40 weeks to await spontaneous labour, with consideration of induction of labour soon after the 40-week mark should labour not occur spontaneously by then.

After delivery, the baby will need close monitoring of its own blood glucose levels, as these can fall after delivery up until when the mother’s milk comes in, which usually occurs late day 3 after delivery.

The baby may need admission to the nursery during this time, and some added feeds with formula for the first few days of life may be needed to maintain the baby’s blood sugar levels until the mother’s milk supply is adequate.

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