Objective: To investigate the metabolic phenotype and pregnancy outcomes of gestational impaired glucose tolerance (IGT) defined by isolated hyperglycemia during an oral glucose tolerance test (OGTT).
Design: Retrospective cohort study.
Setting: University referral hospital.
Population: A total of 4,789 women were screened for gestational diabetes mellitus (GDM) between 1996 and 2008 with a glucose challenge test (GCT), followed by a 2-hour 75-g OGTT if the GCT result was abnormal; in addition, measurement of plasma insulin concentration during the OGTT was implemented from 2004.
Methods: The insulin sensitivity (IS(OGTT)) and beta-cell function (insulinogenic index/homeostasis model assessment for insulin resistance) were calculated for 283 women who underwent a diagnostic OGTT between 2004 and 2008. Perinatal complications were examined in 4,789 women who were screened for GDM between 1996 and 2008.
Main outcome measures: Comparison of outcomes among women stratified by glucose tolerance status using the GCT and OGTT profiles.
Results: Insulin sensitivity and beta-cell function significantly decreased from normal OGTT to 2-hour IGT (single hyperglycemia at 2 hours) to 1-hour IGT (single hyperglycemia at 1 hour) to GDM, with significant differences between normal OGTT and 1-hour IGT or GDM. The occurrence of large-for-gestational age (LGA) neonates was significantly increased in women with GDM or 1-hour IGT (adjusted odds ratio: 2.15, 2.22; 95% confidence interval 1.23-3.75 and 1.04-4.35, respectively) compared to those with normal GCT or normal diagnostic OGTT results.
Conclusions: Like GDM, isolated 1-hour hyperglycemia on the OGTT is associated with beta-cell dysfunction and an increased risk for LGA neonates.