At present the diagnosis of gestational diabetes uses differing criteria in different parts of the world, with none being based on pregnancy outcome. Different glucose loads (50, 75 or 100 grams) are recommended, rather than the standard 75 gram load utilized worldwide in nonpregnant individuals. The HAPO study was designed to determine what level of glucose intolerance, short of diabetes, is associated with an excess of adverse perinatal outcomes. On a 75 gram, 2-hour OGTT each of the 3 values is significantly and continuously related to various adverse outcomes, and no inflection point is evident. Consequently an international group of interested experts is developing recommendations for diagnostic criteria for GDM which, it is hoped, will be adopted world wide.