The diagnosis of "pathological hyperglycaemia' in gestational diabetes in a high risk obstetric population

In order to define a level of "pathological hyperglycaemia', i.e. glucose intolerance that predicts perinatal morbidity among the obstetric population, 100 g glucose tolerance tests (GTTs) were performed in 660 patients attending for antenatal care at the University Hospital in Jeddah. The results were analysed in two ways: (1) patients were stratified according to the number of abnormal glucose values on the GTTs and (2) patients were placed into one of three groups according to the 100 g GTT diagnostic criteria, i.e. normal (non-GDM), abnormal with fasting blood glucose (FBG) > or = 5.8 mmol l-1 (GDM), and abnormal with FBG < 5.8 mmol l-1 (gestational induced hyperglycaemia, GIH). Although there was a stepwise association between fetal/maternal morbidity with increasing number of abnormal glucose values, no level of glucose intolerance could be defined as a threshold level for normal response. However, when stratified by FBG, GDM patients were significantly heavier (78.5 kg +/- SD 14.9), had a higher incidence of both macrosomia (27.5%) and operative delivery (25.3%) than the other two groups (14.7%, 14.3%, and 15.4%, 12.8% in the non-GDM and GIH, respectively). It is suggested that among patients with abnormal GTT results a FBG > or = 5.8 mmol l-1 identifies a threshold for true "pathological hyperglycaemia'.