Isolated hyperglycemia at 1 hour on oral glucose tolerance test in pregnancy resembles gestational diabetes mellitus in predicting postpartum metabolic dysfunction

Abstract

Objective: Gestational impaired glucose tolerance (GIGT), defined by a single abnormal value on antepartum 3-h oral glucose tolerance test (OGTT), is a metabolically heterogeneous disorder. Indeed, the antepartum metabolic phenotype of women with a single abnormal value at 1 h during the OGTT (1-h GIGT) resembles that of women with gestational diabetes mellitus (GDM), whereas GIGT at 2 or 3 h (2/3-h GIGT) is similar to normal glucose tolerance (NGT). Thus, we hypothesized that 1-h GIGT would be associated with the same adverse outcomes as GDM, i.e., increased infant birth weight and postpartum metabolic dysfunction.

Research design and methods: A total of 361 women underwent an antepartum glucose challenge test (GCT) and a 3-h OGTT, assessment of obstetrical outcome at delivery, and metabolic characterization by OGTT at 3 months postpartum. The antepartum GCT/OGTT identified five study groups: GDM (n = 97), 1-h GIGT (n = 28), 2/3-h GIGT (n = 34), abnormal GCT NGT (abnormal GCT with NGT on OGTT) (n = 128), and normal GCT NGT (normal GCT with NGT on OGTT) (n = 74).

Results: Caesarian section rate was higher in women with 1-h GIGT, but birth weight did not differ significantly between the non-GDM groups (P = 0.1978). At 3 months postpartum, glycemia (area under the glucose curve) progressively increased across the groups from normal GCT NGT to abnormal GCT NGT to 2/3-h GIGT to 1-h GIGT to GDM (P < 0.0001), while both insulin sensitivity (IS(OGTT)) and beta-cell function (insulinogenic index/homeostasis model assessment of insulin resistance [HOMA-IR]) progressively decreased (P = 0.002 and P < 0.0001, respectively). The strongest independent negative predictors of insulinogenic index/HOMA-IR were GDM (t = -4.1, P < 0.0001) and 1-h GIGT (t = -3.8, P = 0.0002).

Conclusions: Like GDM, 1-h GIGT is associated with postpartum glycemia, insulin resistance, and beta-cell dysfunction.

Figure 1—

Glycemia, insulin sensitivity, and β-cell function at 3 months postpartum per glucose tolerance group in pregnancy. A: AUC_gluc, trend P < 0.0001; GDM vs. normal GCT NGT, P < 0.0001; 1-h GIGT vs. normal GCT NGT, P = 0.0002; 2/3-h GIGT vs. normal GCT NGT, P = 0.0012; abnormal GCT NGT vs. normal GCT NGT, P = 0.0581; GDM vs. abnormal GCT NGT, P < 0.0001; and 1-h GIGT vs. abnormal GCT NGT, P = 0.0551. B: IS_OGTT, trend P = 0.002; GDM vs. normal GCT NGT, P = 0.0217; and 1-h GIGT vs. normal GCT NGT, P = 0.0212. C: Insulinogenic index/HOMA-IR, trend P < 0.0001; GDM vs. normal GCT NGT, P < 0.0001; 1-h GIGT vs. normal GCT NGT, P = 0.0001; GDM vs. abnormal GCT NGT, P = 0.0179; and 1-h GIGT vs. abnormal GCT NGT, P = 0.0178. (For each box-and-whisker plot: line inside box indicates median, upper and lower limits of box indicate 75th and 25th percentiles, upper and lower bars indicate maximum and minimum values, and plus sign indicates mean.)