Screening for hyperglycaemia in pregnancy

All pregnant women without diagnosed diabetes should be tested for hyperglycaemia in pregnancy¹.

Women at higher risk of hyperglycaemia in pregnancy (see Risk factors for hyperglycaemia in pregnancy (including gestational diabetes)) should be tested early in pregnancy—around the time of the first antenatal visit. Testing aims to detect previously undiagnosed diabetes, so that women with blood glucose concentrations reaching the threshold for diagnosis of diabetes can receive prompt antihyperglycaemic treatment. Glycated haemoglobin (HbA1c) or fasting blood glucose concentrations are suitable for early testing. Oral glucose tolerance testing is usually not undertaken during the first trimester. However, if there are clinical concerns, a test for hyperglycaemia in pregnancy using an oral glucose tolerance test can be performed at any time during pregnancy.

If a woman at higher risk has a normal HbA1c or fasting blood glucose concentration test result, she should have repeat testing with a 75 g oral glucose tolerance test at the same time as a woman who is not at higher risk is tested.

Women who are not at higher risk for hyperglycaemia in pregnancy should be tested for diabetes at 24 to 28 weeks’ gestation using a 75 g oral glucose tolerance test (see Oral glucose tolerance testing for hyperglycaemia in pregnancy). The aim should be to test as close to 28 weeks’ gestation as possible because testing at 24 to 26 weeks’ gestation may miss some women who develop abnormal glucose tolerance later.

At the time of writing, it is unclear whether diagnosis and management of early gestational diabetes in the second trimester (before 24 weeks’ gestation) improves pregnancy outcomes. However, early gestational diabetes diagnosed before 24 weeks’ gestation is associated with more adverse pregnancy outcomes than gestational diabetes diagnosed at the usual testing time (between 24 and 28 weeks’ gestation).