What are the recommended screening protocols for gestational diabetes in pregnant women?

For pregnant women, the screening protocols for gestational diabetes mellitus (GDM) involve assessing risk factors and conducting specific tests.

• Risk Assessment: At the booking appointment, assess for risk factors including a BMI above 30 kg/m², a previous macrosomic baby weighing 4.5 kg or more, previous gestational diabetes, a family history of diabetes (first-degree relative), or an ethnicity with a high prevalence of diabetes ¹,²,³. Women with any of these risk factors should be offered testing for gestational diabetes ¹. Do not use fasting plasma glucose, random blood glucose, HbA1c, glucose challenge test, or urinalysis for glucose to assess the risk of developing GDM ¹.
• Testing Protocol: The recommended test for gestational diabetes is the 75-g 2-hour oral glucose tolerance test (OGTT) ¹.
• Timing of Testing:
  • For women who have had gestational diabetes in a previous pregnancy, offer early self-monitoring of blood glucose or a 75-g 2-hour OGTT as soon as possible after booking (whether in the first or second trimester) ¹. A further 75-g 2-hour OGTT should be offered at 24 to 28 weeks if the results of the first OGTT are normal ¹.
  • For women with any other risk factors for gestational diabetes, a 75-g 2-hour OGTT should be offered at 24 to 28 weeks ¹.
  • Consider further testing to exclude gestational diabetes in women who have glycosuria of 2+ or above on one occasion, or glycosuria of 1+ or above on two or more occasions, during routine antenatal care ¹.
• Diagnosis: Gestational diabetes is diagnosed if the woman has either a fasting plasma glucose level of 5.6 mmol/litre or above, or a 2-hour plasma glucose level of 7.8 mmol/litre or above ¹. When GDM is diagnosed, women should be offered a review with the joint diabetes and antenatal clinic within one week, and their primary healthcare team should be informed ¹.