We evaluated glucose tolerance during the first year postpartum in 113 women with gestational diabetes mellitus (GDM) diagnosed according to the criteria of the First International Workshop-Conference on GDM and the National Diabetes Data Group. The high incidence of abnormal postpartum glucose tolerance (38% “diabetes mellitus” plus 19% “impaired glucose tolerance”) was correlated with certain of the heterogeneous characteristics of the population at the time of antepartum diagnosis. Virtually all women with antepartum fasting plasma glucose (FPG) >130 mg/dl (GDM class BO remained abnormal postpartum (21/22 [95%]), which suggests that this group may include women with preexisting glucose intolerance unrecognized before pregnancy. In the remainder, those with FPG > 105–129 mg/dl (GDM class A2) were more likely to be abnormal postpartum than those with FPG <105 mg/dl (GDM class A,). Within the A, and A2 groups, increasing maternal age, relative insulinopenia, and hyperglycemia at 2 h during antepartum OGTT were also associated with a greater likelihood of abnormal glucose tolerance postpartum. The presence of HLA-DR3 and/or -DR4 antigens was not predictive of the status of glucose tolerance during the first year postpartum, although the increased frequency of cytoplasmic islet cell antibodies in A2 and B1 subjects was associated with a high incidence of abnormal postpartum glucoregulation.
The high incidence of abnormal postpartum glucose tolerance in all GDM classes makes a compelling case for careful, early, and continuing follow-up of all women with a diagnosis of GDM. The risks of abnormal glucose tolerance in the first year postpartum appear to be correlated with some of the heterogeneous characteristics of women with GDM. Differences in such genotypic and phenotypic features as we have analyzed may account for differences in the incidence of postpartum abnormality in different populations. They must be considered in all studies attempting to elucidate the pathophysiology of GDM or to evaluate therapeutic strategies designed to alter the prognosis for glucoregulation under nongravid conditions.