 Gestational diabetes mellitus GDM is a common complication of pregnancy. Multiple treatment regimens are currently used for the management of GDM. Following failure of diet therapy, insulin, glyburide and metformin are all used in the treatment of GDM with the oral medications providing comparable outcomes with insulin but easier route of administration and schedule. The proposed work will evaluate the pharmacokinetics PK and pharmacodynamics PD of glyburide and metformin alone and in combination in order to lay the foundation in establishing dosage and response information that could be utilized in designing a phase III randomized trial that will ultimately evaluate GDM treatment optimization. 