 All women receiving prenatal care at Vanderbilt University Medical Center who do not already carry a diagnosis of type 1 or type 2 diabetes are screened for GDM between weeks 24-28 of pregnancy with a non-fasting 50-gram glucose tolerance test GTT. Blood glucose values greater than or equal to 140 on this screening test are considered positive. Women with a positive screening test undergo a diagnostic fasting 100-gram 3-hour GTT. GDM is diagnosed if a woman has 2 or more abnormal values on the 3-hour GTT abnormal values are fasting blood glucose greater than or equal to 95, 1-hour blood glucose greater than or equal to 180, 2-hour blood glucose greater than or equal to 155 andor 3-hour blood glucose greater than or equal to 140. By reviewing the electronic medical record of women with singleton pregnancies undergoing GTT on a weekly basis, we will identify women with and without GDM. 