A Serial Study of Changes Occurring in the Oral Glucose Tolerance Test During Pregnancy

Summary Nineteen healthy pregnant women with no family history of diabetes took part in a serial study in which they had a standard 50 g. oral glucose tolerance test (OGTT) at 10, 20, 30 and 38 weeks gestation and again 10 to 12 weeks after delivery. While every test result remained within “normal” limits as defined by any of the standard criteria, subtle and progressive changes in the shape of the glucose response curve were shown to occur throughout pregnancy. These changes in shape were evaluated by means of the H index recently described by Billewicz et al . (1973); in 14 patients the values attained were characteristic of a “suspect” or “abnormal” response in non–pregnant subjects. Nevertheless since all of these women remained clinically normal throughout, and it is unlikely that 14 out of 19 will become diabetic later in life, it seems unreasonable that these changes per se should be regarded as evidence of impending pathology.