Islet Function in Gestational Diabetes

Inclusion Criteria: * Pregnant individuals with a viable singleton pregnancy who have completed second trimester gestational diabetes screening and are eligible for classification as either gestational diabetes mellitus or no gestational diabetes mellitus. * Participants must be willing and able to provide informed consent and complete planned pregnancy and postpartum study visits. Exclusion Criteria: * Active systemic illness (e.g. chronic kidney disease, hypertension) * Pre-pregnancy diabetes mellitus * Multiple gestation, major fetal anomaly, or non-viable pregnancy on ultrasound * Fasting glucose ≥ 100 mg/dL or HbA1c ≥ 5.7% in early pregnancy * One abnormal value on the 3-hour 100 g oral glucose tolerance test * Glucose at least 190 mg/dL on glucose challenge testing without subsequent 3-hour oral glucose tolerance testing * Use of medication affecting glucose metabolism before pregnancy or in early pregnancy * Use of glucose-lowering medication (e.g. metformin, glyburide) other than insulin to treat gestational diabetes mellitus in the current pregnancy * History of upper gastrointestinal surgery that alters gastric emptying (e.g. bariatric surgery) * Hemoglobin \< than 11 g/dL