Is there a role for oral antihyperglycemics in gestational diabetes and type 2 diabetes during pregnancy?

Diabetes mellitus is a heterogeneous disorder of glucose intolerance that is generally classified into the following categories: type 1 and type 2 diabetes and gestational diabetes (GDM). Currently, the number of pregnancies complicated by type 2 diabetes and GDM exceed those affected by type 1 diabetes. Numerous studies have established a direct relationship between maternal glycemic control and neonatal outcomes for all types of diabetes. Therefore, modern treatment protocols during pregnancy emphasize strict glycemic control by a combination of diet and medication. Traditionally, insulin therapy has been considered the gold standard for management because of its efficacy in achieving tight glucose control and the fact that it does not cross the placenta. Since GDM and type 2 diabetes are characterized by insulin resistance and relatively decreased insulin secretion, treatment with oral antihyperglycemic agents that target these defects is of potential interest. However, because of concerns regarding transplacental passage and, therefore, the possibility of fetal teratogenesis and prolonged neonatal hypoglycemia, these agents are not currently recommended in pregnancy. There are no randomized controlled trials on which to draw conclusions regarding the teratogenicity of these oral agents. However, most retrospective studies and the published clinical experience have not demonstrated an increased risk of malformed infants among women treated with oral antihyperglycemic agents. Rather, the data indicate that the increased risk for major congenital anomalies appears to be related to maternal glycemic control prior to and during conception. These studies and currently available data on the use of both metformin and sulfonylureas in pregnancy have also failed to demonstrate an increased risk of neonatal hypoglycemia and other neonatal morbidities. To date, there has only been one randomized controlled trial to test the effectiveness and safety of sulfonylurea therapy (glyburide [glibenclamide]) in the management of women with GDM. Both the insulin- and glyburide-treated women were able to achieve satisfactory glucose control and had similar perinatal outcomes. Glyburide was not detected in the cord serum of any infant in the glyburide group. In summary, based on the currently available data, it appears that glyburide could be safely and effectively utilized in the management of GDM. However, more intensive investigation regarding the safety and feasibility of oral agents in pregnancies complicated by type 2 diabetes is necessary. It is important to emphasize that it is the level of metabolic control achieved and not the mode of therapy that is crucial to improving outcomes in these pregnancies.