The Oral 100-g-Glucose-Tolerance Test— Special Criteria for Evaluation in Late Pregnancy

Abstract

If a disorder of carbohydrate metabolism in pregnancy is suspected, an oral glucose tolerance test is usually performed. If 100 g glucose are used, the test results are generally interpreted according to the so-called pregnancy-specific norm criteria of O’Sullivan and Mahan (1964). An indication for the test most often appears in the third trimester. Even if a test was already performed in early pregnancy and found to be normal, it should be repeated at this time. This is because the chance of revealing a disorder seems greatest in the third trimester, in which a marked deterioration of oral glucose tolerance is physiologic (Kühl, 1975; Lind et al., 1973). The question arises whether the oral 100-g-glucose-tolerance test performed in the third trimester can be adequately evaluated by the criteria of O’Sullivan and Mahan (1964). These criteria are based on investigations only half of which were done in the third trimester, while the rest were done earlier in pregnancy. The increasing alterations of carbohydrate metabolism, particularly in the second half of pregnancy make it seem necessary to evaluate the oral 100-g-glucose-tolerance test in late pregnancy according to criteria based on investigations exclusively in this period. Otherwise, we may find an unduely high rate of abnormal glucose-tolerance tests, which, in turn, might lead to an underestimation of its clinical relevance. This investigation aimed to describe the limits of the oral 100-g-glucose-tolerance test in the third trimester of normal pregnancy. The test was performed in a large unselected group of pregnant women in the third trimester at the Universitäts-Frauenklinik Bonn. The associations between the test results and special features of the mother and the newborn were studied, and a control group of pregnant women without diabetic risk factors and with clinically healthy new-borns was established retrospectively.