Screening women who had gestational diabetes

Women who have had gestational diabetes (as defined in Diagnostic thresholds for hyperglycaemia in pregnancy (including gestational diabetes)) should have an oral glucose tolerance test. This should usually be undertaken at 6- to 12-weeks postpartum but may be delayed until 4- to 6-months postpartum if not practical (eg breastfeeding mothers who cannot leave their baby for the 3 hours required for testing).

If the oral glucose tolerance test is normal, it is recommended that the woman has a fasting venous blood glucose concentration and HbA1c measured every year, or an oral glucose tolerance test every 2 to 3 years; if further pregnancy is considered or planned, oral glucose tolerance testing is preferred. An oral glucose tolerance test should also be performed before any planned pregnancies.

If an HbA1c test is used for ongoing screening of women who had gestational diabetes, consider the following when interpreting the result:

• if further pregnancy is considered or planned and the HbA1c is 37 to 46 mmol/mol (5.5 to 6.4%), additional testing with an oral glucose tolerance test is required to detect impaired glucose tolerance, so that it can be managed appropriately before conception
• if there is no likelihood of another pregnancy and the HbA1c is less than 48 mmol/mol (6.5%), ongoing screening for type 2 diabetes should follow the usual schedule for screening people at risk of developing type 2 diabetes (see Screening for type 2 diabetes in asymptomatic adults). Patients with an HbA1c of 42 to 46 mmol/mol (6.0 to 6.4%) may require additional testing to determine if they have impaired fasting glucose or impaired glucose tolerance; see Interpreting HbA1c diagnostic tests.