The Australasian Diabetes in Pregnancy Society (ADIPS) had previously set out guidelines for the testing and diagnosis of gestational diabetes mellitus (GDM) in 1991. However, as a result of the accumulation of more evidence about the incidence and effects of diabetes in pregnancy, ADIPS have revised the guidelines to reflect this new information.
The most important new study was the Hyperglycemia and Adverse Pregnancy Outcome study (HAPO) published in 2008. This was a large, well-performed, multinational study that examined pregnancy outcomes in 23,316 women whose plasma glucose levels were greater than or equal to (≥) 5.8 mmol/L fasting and less than or equal to 11.1 mmol/L 2‐hrs post 75g oral glucose load at 24-28 weeks of pregnancy. The HAPO study found that these women with moderately elevated blood glucose levels during pregnancy had a higher incidence of adverse effects on both the baby and the mother.
The new guidelines have eliminated the old glucose challenge test and recommend that all women have a standard glucose tolerance test (GTT) between 28-28 weeks of pregnancy.
New recommended diagnostic criteria for GDM after a GTT
Fasting glucose level ≥ 5.1 mmol/L
1‐hr glucose level ≥ 10.0 mmol/L
2‐hr glucose level ≥ 8.5 mmol/L
The diagnosis of GDM is made if one or more of these values are abnormal.
The new guidelines will result in a higher proportion of women being diagnosed than was previously the case. The current prevalence of gestational diabetes is about 9%. Studies in Australia have shown that gestational diabetes will now be diagnosed in about 12% to 13.5% of pregnant women. This is a 50% increase in the number of women who will need treatment for diabetes during their pregnancy. In many cases this treatment will consist of women being very careful about their weight and diet during the pregnancy and also following an exercise program. However in some cases insulin injections may be required as well. Monitoring blood glucose levels at home using finger-prick samples and a blood glucose meter will be part of the management program.
Some women who are higher risk of developing GDM should have earlier testing. These women at higher risk include:
• Previous gestational diabetes mellitus (GDM)
• Ethnicity: Asian (including Indian), Aboriginal, Pacific Islander, Maori, Middle Eastern, non‐white African
• Maternal age ≥40 years
• Family history of diabetes (first degree relative with diabetes including a sister with GDM)
• Obesity, especially if BMI > 35 kg/m2
• Previous baby with birth weight more than 4500 g
• Women on medications: corticosteroids, antipsychotics
Women who are diagnosed with GDM will need to be extra careful and watch for GDM in future pregnancies and also during later life as they have a higher risk of developing type 2 diabetes as they get older than other women.