Gestational Diabetes Mellitus (GDM) is defined as any degree of glucose intolerance with onset at or first detected during pregnancy.  It affects around 9% of women who are pregnant and the incidence is increasing because it mirrors the higher incidence of Type 2 diabetes in younger people in more affluent nations.  The reason could be related to more women entering pregnancy being overweight as well as eating more calories during the pregnancy. 

Click to view Diabetes SA video on What is Gestational Diabetes

Cause of Gestational Diabetes Mellitus

Gestational diabetes usually manifests around the 2nd half of the pregnancy.  Your doctor may advise you to have a Oral Glucose Tolerance Test (OGTT) at around 24 weeks gestation if you are at risk or show signs of GDM.   Diabetes occurs because there is;

• Insufficient insulin secretion during pregnancy
• Reduction in peripheral sensitivity to insulin

Who is at risk for Gestational Diabetes?

• History of GDM in previous pregnancies
• Multiple pregnancies (twins or triplets)
• Being overweight (BMI more than 27)
• Increased maternal age
• Family history of diabetes
• History of macrosomia (birth weight of previous babies more than 4 kg)

Screening Criteria from Different Countries

How is Gestational Diabetes Diagnosed?

You will normally have a Fasting Blood Glucose (FBG) and HbA1c measured during your 1st Pre-Natal visit.  If you are at risk of developing GDM, you may need to do a OGTT during this first visit.

1. Overt Diabetes in Pregnancy

• FBG 7 mmol/l or more
• HbA1c 6.5% or more
• Random blood glucose 11.1 mmol/l or more

2. Gestational Diabetes

Oral Glucose Tolerance Testing (OGTT) may be performed at 24-28 weeks gestation and a diagnosis of Gestation Diabetes will be made if your blood tests show

• FBG 5.1-6.9  mmol/l or more
• BG 10.0 mmol/l or more 1 hour post-prandial (75 gm OGTT)
• BG 8.5 mmol/l (some Drs use 7.8 mmol/l) or more 2 hours post-prandial (75 gm OGTT)

Discuss with your gynae doctor, endocrinologist and dietician about

your treatment options for your Gestational Diabetes

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