What are the risk factors for gestational diabetes mellitus that should be assessed at the booking appointment?

At the booking appointment, assess all pregnant women for these GDM risk factors: BMI above 30 kg/m2, previous macrosomic baby over 4.5 kg, previous gestational diabetes, family history of diabetes in a first-degree relative, and ethnicity with a high prevalence of diabetes. If any risk factor is present, offer a 75g 2-hour oral glucose tolerance test at 24 to 28 weeks' gestation; for previous GDM, offer early testing as soon as possible after booking.

The booking assessment for gestational diabetes should include checking each of the listed risk factors in every pregnant woman. These are a BMI above 30 kg/m2, having previously given birth to a macrosomic baby weighing more than 4.5 kg, a history of gestational diabetes in a previous pregnancy, a first-degree family history of diabetes, and belonging to an ethnic group with a high prevalence of diabetes. Additional consideration for testing is triggered by glycosuria: 2+ on one occasion or 1+ on two occasions. When at least one of the formal risk factors is identified, the woman should be offered a 75 g 2-hour oral glucose tolerance test at 24 to 28 weeks of gestation. If the risk factor is a previous gestational diabetes pregnancy, offer early self-monitoring of glucose levels or an early OGTT soon after booking, with a repeat OGTT at 24 to 28 weeks if the early test is normal. If GDM is diagnosed early, obtain HbA1c to screen for possible undiagnosed type 2 diabetes.