Gestational Diabetes Mellitus Trial (GDM)

Gestational diabetes mellitus is defined as glucose intolerance of variable severity with onset or first recognition during pregnancy. The definition applies regardless of insulin use for treatment or the persistence of the condition after pregnancy, and does not exclude the possibility that unrecognized glucose intolerance or overt diabetes may have preceded the pregnancy. Pre-existing diabetes substantially contributes to perinatal morbidity and mortality. The association of milder forms of gestational diabetes with adverse pregnancy outcomes, including morbidities such as macrosomia, birth trauma, and neonatal hypoglycemia, remains questionable. While it is likely that maternal glucose intolerances reflect a continuum of risk for adverse outcomes, it is not known whether there is a benefit to identification and subsequent treatment of mild glucose intolerance during pregnancy. This study will determine whether dietary treatment (and insulin as required) for mild GDM will reduce the frequency of neonatal morbidity associated with mild glucose intolerance. Participants in this study will receive a 50-gram glucose loading test (GLT) between 24 and 30 weeks' gestation. Those with a positive GLT will receive a subsequent 3-hour oral glucose tolerance test (OGTT). Based upon these test results, women will be assigned to 4 groups. Women with a positive GLT and abnormal OGTT will be randomly assigned to receive either nutritional counseling and diet therapy (Group 1) or no specific treatment (Group 2a). Women with a positive GLT but normal OGTT will be enrolled in Group 2b for observation. Women with a negative GLT will be enrolled in Group 3 and will serve as a control group. Women in Group 1 will receive formal nutritional counseling and will be instructed on the techniques of self blood glucose monitoring. Patients will take daily blood glucose measurements and will be seen at weekly study visits. The study will evaluate birth outcomes, including stillbirth, neonatal hypoglycemia, neonatal hyperinsulinemia, neonatal hyperbilirubinemia, and birth trauma. The follow-up study will examine if blood sugar levels and treatments during pregnancy influence the health of the mother and child several years later. The study will also examine whether there is a genetic link to the health of the mother and child. The study visit will include blood pressure, body size measurements, blood draw and saliva collection, and questions related to the mother and child's health and environment.