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