Gestational impaired glucose tolerance, defined by a single abnormal value at 1 hour during the oral glucose tolerance test, is associated with many of the same adverse outcomes as gestational diabetes mellitus, including postpartum glycemia, insulin resistance, and b-cell dysfunction.
Investigators evaluated the obstetric outcomes of postpartum metabolic function in a cohort of more than 360 women stratified by glucose tolerance status during pregnancy. The women underwent an antepartum glucose challenge test (GCT) and a 3-hour oral glucose tolerance test (OGTT), an assessment of obstetric outcome at delivery, and a metabolic characterization by OGTT at 3 months post partum.
Five study groups were identified: those with gestational diabetes mellitus (GDM), 1-hour gestational impaired glucose tolerance (GIGT), 2- or 3-hour GIGT, abnormal glucose challenge test (GCT) with normal glucose tolerance (NGT), and normal GCT with NGT (Diabetes Care 2008;31:1275–81).
There were no significant differences among the groups with respect to mean age, smoking status, and parity.
The researchers noted the 1-hour GIGT group had adverse outcomes similar to the group with gestational diabetes mellitus, although the GIGT group did not have increased infant birth weight. The c-section rate was highest in the 1-hour GIGT group, but there were no significant differences among the four non-GDM groups, wrote Dr. Ravi Retnakaran of the Leadership Sinai Centre for Diabetes, Mount Sinai Hospital, Toronto, and the division of endocrinology and metabolism at the University of Toronto, and his colleagues. There were also no significant differences among the four non-GDM groups with respect to length of gestation, infant sex, or Apgar scores.
At 3 months post partum, glycemic parameters progressively increased from normal glucose challenge test with normal glucose tolerance to abnormal glucose challenge test with normal glucose tolerance to 2- or 3-hour gestational impaired glucose tolerance to 1-hour GIGT to gestational diabetes mellitus. Insulin sensitivity and β-cell function progressively decreased across the groups in the same manner.
Participants in the normal GCT NGT group underwent the 3-hour oral glucose tolerance test at a median of 32 weeks' gestation, compared with a median of 29 weeks' gestation for the other four groups.
One limitation of the current study was the small number of subjects with GIGT (28). Still, the authors said further investigation is warranted to determine the risk of type 2 diabetes and to conduct a cost-benefit evaluation of postpartum care strategies.
The study was supported by a grant from the Canadian Institutes of Health Research.