Plasma glucose responses during the 75-g OGTT were found to be lower than those during the 100-g OGTT. When using the same diagnostic criteria, the prevalence of GDM was also found lower using the 75-g glucose load. It would therefore not be appropriate to use the 75-g OGTT for diagnosing GDM using the criteria and reference values of the 100-g OGTT. To give a comparable prevalence of GDM, the threshold of abnormal plasma glucose levels of the 75-g OGTT would need to be lower than that of the 100-g OGTT.