This is a pilot feasibility study of 40 pregnant women to test the investigators' recruitment, enrollment and randomization procedures in preparation to conduct a larger randomized control trial to compare diagnostic methods for gestational diabetes. The two methods that are being compared are the 2 hour 75 gram OGGT (2011 ADA guidelines) versus a 1 hour 50 gram GCT + 3 hour 100 gram OGTT if the 1 hour result is abnormal (Carpenter and Coustan criteria).

This is a pilot feasibility study of 40 pregnant women between 24-28 weeks gestation to test the investigators recruitment, enrollment and randomization procedures in preparation to conduct a larger randomized control trial to compare diagnostic methods for gestational diabetes.

Forty women 18 years of age or older will be recruited at 20-24 weeks pregnancy from the ob/gyn outpatient practices at Magee-Women's hospital (MWH). Eligible women will return to MWH main lab between 24-28 weeks gestation for the routine 1 hour 50gm glucose challenge test. Women with blood glucose values less than 200 will be randomized to receive either the fasting 2 hour 75 gm oral glucose tolerance test (OGTT)or the 3 hour 100 gm OGGT within two weeks. Gestational diabetes will be determined for the 2 hour 75 gm OGGT arm based on the 2011 ADA guidelines and the 3 hour 100 gm OGGT arm based on the Carpenter and Coustan criteria. Patients and their providers will be informed of the diagnosis of gestational diabetes, but they will be blinded to the criteria used to make the diagnosis as well as the specific results of glucose tolerance testing.

Chart reviews will be conducted to assess for perinatal maternal and infant health factors (e.g.pregnancy weight, gestational weight gain, co morbidities) as well as for data on perinatal outcomes related to GDM such as macrosomia, c-sections, and birth trauma. Two brief self-administered questionnaire will assess participants' views on screening for gestational diabetes and assess participants experience with and solicit feedback on the study procedures.

At the end of this pilot study, the investigators will have experience with recruitment, retention, and randomization procedures and have made the necessary protocol revisions. If successful, this feasibility study will provide the preliminary data and feasibility justification needed to conduct a larger randomized control trial to compare the effectiveness of two diagnostic methods for gestational diabetes.

Inclusion Criteria:

• Singleton pregnancy
• Plan to undergo gestational diabetes screening at 24-28 weeks' gestation.

Exclusion Criteria:

• Existing Type 1 or Type 2 diabetes
• Diabetes diagnosed early in pregnancy (less than 24 weeks gestation)
• Multiple gestation (e.g. twins, triplets)
• Chronic hypertension (requiring medications)
• Oral, IM or IV corticosteroid use within the previous 30 days
• Major congenital anomaly or anticipated preterm delivery before 28 weeks
• Inability to complete 50 gram GCT before 28 completed weeks' gestation
• Patients with known HIV, Hepatitis B or C virus.