Methods for the screening and diagnosis of gestational diabetes mellitus between 24 and 28 weeks of pregnancy.

The aim of this review is to provide answers to the question “How does one screen for and diagnose gestational diabetes mellitus (GDM) between 24 and 28 weeks gestation?” Two methods are currently widely used: a one-step approach (the 75g-Oral Glucose Tolerance Test, OGTT) and a two-step approach (the 50g Glucose Challenge Test, GCT, followed by 100g-OGTT). A review of the literature showed that both methods had good reproducibility (around 80%), whilst neither required preliminary diet changes. The data of the Hyperglycaemia Adverse Pregnancy Outcomes (HAPO) study on materno-foetal morbidity provided consistent support in favour of the 75g-OGTT. In addition, this one-step method presents several advantages over the two-step method, i.e. it provides a faster diagnosis time, better tolerance and it is easier to remember. We thus recommend a 75g-OGTT including three measures of the glycaemia at times 0, 1 and 2 hours for the diagnosis of GDM between 24-28 weeks of pregnancy. A discussion of alternative methods revealed that measuring Fasting Glycaemia (FG) between 24 and 28 weeks of pregnancy was unsuitable, and that measuring HbA1c, fructosamine, glycosuria, or random and postprandial plasma glucose was not advisable. This is based on the fact that too few studies have evaluated these methods, and that the studies usually involved heterogeneous populations in varying numbers, using differing criteria and sensitivity values. However, HbA1c measurements may prove useful in detecting pre-pregnancy diabetes mellitus.