(748) The effect of glucose challenge and oral glucose tolerance tests timing on tests' results

The usual time for performing glucose challenge test (GCT) and oral glucose tolerance test (OGTT) is between 24-28 gestational weeks. After which, it is not known whether GCT or OGTT act in the same manner.

In the present study we compared the results of GCT and OGTT when the tests were done between 24-28 gestational weeks or later.   

Study Design:

A population-based retrospective cohort study of women who performed GCT between June 2013 and December 2021. In our institution GCT is recommended even after 28.6 weeks to women who did not perform it before. Women with large for gestational age fetus or polyhydramnios were excluded, since OGTT is performed in those cases. The rates of abnormal GCT (≥140 mg%) and gestational diabetes mellitus (GDM) were compared. GDM was defined as GCT≥200 mg% or at least 2 abnormal OGTT values according to the Carpenter and Coustan criteria.

Results:

Data were collected for 20,485 women with GCT between 24-28.6 weeks and 1,806 with GCT thereafter. GCT results for every gestational week are presented in the figure. The rate of abnormal GCT and GDM were similar between the groups (abnormal GCT: 3797 (18.5%) versus 323 (17.9%), respectively; P=0.49, and GDM: 1063 (5.2%) versus 86 (4.8%), respectively; P=0.43)

Conclusion:

In low risk women, GCT values and the rate of GDM are similar from 24 weeks and thereafter.