Diabetes complicating pregnancy

Abstract

Despite the well-documented relationship between morbidity in pregnancy and pregestational maternal diabetes, the corrected perinatal outcome is, in most series, equal to or better than that of the general reference obstetric population. No single aspect or element of contemporary management is responsible for this improvement; rather, a combination of interventions seems responsible. Targeting delivery early in term, improved compliance, better glycemic control during pregnancy, improved control at conception, improved neonatal care, family planning, and early screening for fetal abnormalities all likely contribute to improved outcome. The currently observed rates of perinatal mortality suggest that an irreducible minimum mortality rate may be reached; however, large disparities in access to care and treatment continue to result in a wide range in rates of morbidity and mortality, a fact that pertains to outcomes in general as well as to pregnancies complicated by diabetes. The identification of women with lesser degrees of hyperglycemia as diabetic by lowering the thresholds for glucose tolerance test abnormality suggests an importance of the diagnosis that is not supported by evidence of either related morbidity or therapeutic benefit. The extrapolation of risk to women with lesser degrees of hyperglycemia seems to have little basis, and the management of women with mild glucose intolerance as if they had overt diabetes is unwarranted. The excess of resources dedicated to the identification and monitoring of an increasing number of women with mild abnormalities of glucose metabolism should prompt a reevaluation of these practices. Perinatal benefits of this expenditure are difficult to document or nonexistent, and there is a predictable increase in iatrogenic morbidities associated with the diagnosis. The exception in the most recent recommendations is the addition of a random glucose measure to screen for the rare women with overt undiagnosed diabetes who presents for prenatal care, because these women are at increased risk of morbidities related to diabetes. A curious statement was made in the summary and recommendations of the fourth International Congress on Gestational Diabetes: "There remains a compelling need to develop diagnostic criteria for GDM [gestational diabetes mellitus] that are based on the specific relationships between hyperglycemia and risk of adverse outcome." If these relationships are undefined, what is the import of the diagnosis? At the author's center, application of the new diagnostic thresholds for the diagnosis of gestational diabetes mellitus has increased the incidence to over 6%. Without a clear expectation of benefit, this increase represents an unsupportable investment of resources. What are the prospects for improving understanding of the relationships between glucose intolerance and pregnancy risks? The direction of new guidelines and recommendations seems to be moving away from resolution of the relationships. The new criteria result in the diagnosis of gestational diabetes in an increasing number of women who were previously normal. It is easier to differentiate women at an extreme of hyperglycemia from normal. Investigations will be even less able to identify attributable effects of glucose intolerance in pregnancy with the inclusion of women with lesser degrees of hyperglycemia. As evidenced in O'Sullivan's original series, women with fasting hyperglycemia in pregnancy are still presumed to be at increased risk of fetal death. This risk factor remains important in clinical management if insulin treatment, fetal surveillance, and early term delivery can reduce the risk of fetal loss. At the author's center, the relationships among outpatient measures of fasting glycemia, glucose tolerance testing results, and perinatal outcomes are evaluated. Preliminary results suggest that fasting glycemia measured at the time of a 50-g glucose tolerance test is significantly correlated with and as sensitive and predictive of morbidity as the glucose tolerance test diagnosis of gestational diabetes. If these results are confirmed, it will be difficult to rationalize continued glucose tolerance testing.