(645) First-trimester fasting glucose levels associated with abnormal glucose challenge and tolerance tests later in pregnancy

Gestational diabetes mellitus (GDM) is diagnosed using an initial glucose challenge test (GCT), and if exceeds 140 mg/dL is followed by an oral glucose tolerance test (OGTT). The definition of pathological first-trimester fasting glucose (FG) is controversial, and its correlation with abnormal GCT and OGTT is not well established. This study aims to evaluate the association between first-trimester FG levels and pathological GCT and OGTT results.

Study Design:

We retrospectively analyzed the electronic medical records of a large healthcare provider searching for individuals who delivered between 2012 and 2024. Inclusion criteria were singleton pregnancies and a documented first-trimester FG, excluding those with preexisting diabetes. Only the first documented pregnancy was included. We assessed the cohort’s distribution of first-trimester FG values and compared the rates of abnormal GCT and OGTT between those with FG above and below the 95th percentile (two standard deviations).  The primary outcome was the incidence of abnormal GCT and OGTT above vs. below the 95th percentile of FG.

Results:

The study comprised 202,960 individuals who met the inclusion criteria. The mean first-trimester FG level was 84.6±9.9 mg/dL, and the 95th percentile was 100 mg/dL. Those with an FG≥100 mg/dL were older and had a higher BMI (31.0±5.7 vs. 29.8±5.5 years, p< 0.001 and 28.2±6.7 vs. 25.1±14.9 kg/m², p< 0.0001, respectively). Moreover, they had higher pathological rates of GCT and OGTT (19.2% vs. 13.1%, p</span>>0.001, and 6.9% vs. 2.4%, p</span>>0.001, respectively). We observed a positive association between increasing FG levels and pathological GCT and OGTT results (Fig. 1).

Conclusion:

First-trimester fasting glucose levels of 100mg/dL or higher are significantly associated with increased rates of pathological glucose challenge test and oral glucose tolerance test. Further consideration should be given to adjusting pregnancy management for these high-risk populations.