First trimester oral glucose tolerance test in a population at high risk for gestational diabetes

Gestational diabetes mellitus (GDM) is defined as glucose intolerance, which is first detected during pregnancy. In the current study, we evaluated whether a first trimester 75 g oral glucose tolerance test (oGTT) is useful in stratifying pregnant women at high risk.

We screened pregnant women at risk by using a 75 g oGTT at first visit. Later on we changed the screening strategy either by measuring random glucose or glycosylated haemoglobin in the first trimester. If the first trimester oGTT was normal, a second 75 g oGTT was performed between 24 and 28 weeks. Fasting, 1h, and 2h glucose values were compared between GDM and non GDM cases. Mann Whitney U test, Chi² test, and ROC analysis were used for statistical purposes.

We included 89 women. Higher first trimester oGTT glucose values were found in women with GDM (fasting GDM: 4.76 vs. non GDM: 4.21; p = 0.0024/1h 8.43 vs. 6.71; p = 0.012/2h 7.02 vs. 5.70; p = 0.0007). The cut-off value was 4.65mmol (LHR 2.61; sensitivity 78.5%, specificity 70%), 7.35mmol (LHR 3; sensitivity 66.7%, and specificity 77.8%), and 6.65mmol (LHR 4.09; sensitivity 81.1%, specificity 80%) for fasting, 1h, and 2h glucose values. The areas under the ROC curve were 0.79 (p < 0.05), 0.83, (p = 0.0012), and 0.83 (p = 0.0006).

The implementation of a oGTT in the first trimester to exclude preexisting diabetes may be useful in discriminating the women who will develop GDM. To investigate on the efficacy of this approach, more studies on a larger sample including low risk women are needed.