Fasting plasma glucose level to guide the need for an OGTT to screen for gestational diabetes mellitus

Abstract

Aims: To determine the fasting plasma glucose (FPG) level at which an oral glucose tolerance test (OGTT) could be avoided to screen for gestational diabetes (GDM) and to evaluate the characteristics of women across this FPG threshold.

Methods: A multi-centric prospective cohort study with 1843 women receiving universal screening for GDM with a 75 g OGTT.

Results: In the total population, GDM prevalence was 12.5% (231). A FPG < 78 mg/dL was the cut-off with best trade-off to limit the number of missed GDM cases [44 (19.0%)] with a negative predictive value of 97.3% (95% CI 96.5-98.0) for GDM, while avoiding 52.2% OGTTs. Compared to GDM with FPG ≥ 78 mg/dL [187 (81.0%)], GDM women with FPG < 78 mg/dL had a significantly lower BMI (27.1 ± 4.5 vs. 29.6 ± 5.2 kg/m², p = 0.003), less insulin resistance [Matsuda: 0.4 (0.4-0.7) vs. 0.3 (0.2-0.5), p < 0.001] and better β-cell function [ISSI-2: 0.13 (0.08-0.25) vs. 0.09 (0.04-0.15), p = 0.004]. Compared to NGT women (1612) with FPG ≥ 78 mg/dL [846 (52.5%)], NGT with FPG < 78 mg/dL [766 (47.5%)] had a significantly lower BMI (26.0 ± 3.9 vs. 27.8 ± 4.7 kg/m², p < 0.001), less insulin resistance [Matsuda: 0.7 (0.5-0.9) vs. 0.5 (0.4-0.7), p < 0.001], better β-cell function [ISSI-2: 0.17 (0.10-0.30) vs. 0.12 (0.07-0.21), p < 0.001], and less often large-for-gestational age infants [9.2 (70) vs. 16.2% (136), p < 0.001].

Conclusions: FPG < 78 mg/dL can be used to limit the number of OGTTs when screening for GDM. Women with FPG < 78 mg/dL had a better metabolic profile and in NGT women also less fetal overgrowth.

Keywords: Fasting plasma glucose; Gestational diabetes mellitus; Pregnancy outcomes; Screening.