Oral glucose tolerance testing at gestational weeks ≤16 could predict or exclude subsequent gestational diabetes mellitus during the current pregnancy in high risk group

Abstract

Background: An oral glucose tolerance test with a result that is negative but close to the diagnostic cut-off in early pregnancy was hypothesized to serve as a predictor of subsequent gestational diabetes in a high risk group. The aim of the study was to determine those cut-off values of OGTT at gestational weeks ≤16, which can predict or exclude subsequent onset of GDM in a high risk group. Methods: Pregnant women at high risk of gestational diabetes ( n = 163) underwent a 2-h, 75-g oral glucose tolerance test at gestational weeks ≤16 were analyzed in this study. In the event of a negative result, subsequent oral glucose tolerance tests were performed at gestational weeks 24–28 and 32–34. The sensitivity, the specificity, the positive and negative predictive values and the Odds ratio of the best cut-off values of fasting and postload glucose levels were calculated. Results: The best cut-off values to exclude subsequent GDM for fasting and postload glucose were 5.0 and 6.2 mmol/l, respectively. In combination, the best cut-off values were 5.3 mmol/l for fasting and 6.8 mmol/l for postload glucose, with negative predictive values of 0.97 and 0.71 and sensitivities of 96.9 and 86.3 at gestational weeks 24–28 and 32–34, respectively. Combination of these cut-off values with obesity proved to be very predictive for gestational diabetes by gestational weeks 32–34, with an Odds ratio of 6.0 [95% confidence interval: 1.7–21.0]. Conclusions: With regard to the very high negative predictive value of the method, pregnant women with glucose levels of ≤5.3 mmol/l at fasting and of ≤6.8 mmol/l at postload in gestational weeks ≤16 should undergo subsequent oral glucose tolerance testing merely at gestational weeks 32–34. Approximately a quarter (24.5%) of the pregnant women at risk of gestational diabetes satisfied these criteria.