The overarching goal of Glycemic Observation and Metabolic Outcomes in Mothers and Offspring (GO MOMs) is to perform a comprehensive, longitudinal description of maternal glycemia over the course of pregnancy and to evaluate how glucose levels throughout pregnancy relate to traditional third trimester gestational diabetes mellitus (GDM) screening and perinatal outcomes.

GO MOMs is an observational study designed to characterize the glycemic profile of pregnancy using continuous glucose monitoring (CGM) technology in order to develop criteria using CGM measurements and/or early pregnancy oral glucose tolerance testing (OGTT) at 10w0d-14w0d gestation that are predictive, along with clinical factors, of adverse pregnancy outcomes in mothers and their newborns. GO MOMs involves multiple institutions and an anticipated 2179 participants. Participants will attend 4 research study visits: Visit 1 (10w0d-14w0d gestation), Visit 2 (16w0d-20w0d gestation), Visit 3 (24w0d-28w0d gestation), and Visit 4 (32w0d-36w0d gestation). Additional data will be collected at a Delivery Visit and via chart abstraction. Mothers will have a Remote Follow-up call after delivery to collect additional data. At Visits 1-4, a blinded CGM sensor will be placed. Participants will be instructed to wear the sensor for 10 days after which time they will follow instructions to return it to their study site. At Visit 1 (10w0d-14w0d gestation), participants will undergo a 75 g 2-hour (hr) OGTT. At Visit 3 (24w0d-28w0d gestation), participants will undergo a 100 g 3 hr OGTT. Visit 1 will include an extended maternal interview to collect social and demographic, medical history, obstetrical history, surgical history, family medical history, current health and pregnancy, and lifestyle (sleep, alcohol, tobacco use) data. Medical history, alcohol and tobacco use data will be updated at each study visit. Sleep data will be updated at Visit 3 (24w0d-28w0d gestation). Blood and urine samples will also be obtained at each visit for additional laboratory testing and some will be stored for ancillary investigations. At the Delivery Visit, newborn physical measurements including weight, length and skinfolds will be performed. Birthweight at delivery will also be obtained through chart abstraction. Primary statistical analyses will be performed to develop predictive criteria based on CGM and/or OGTT measures at Visit 1 (10w0d-14w0d gestation) along with clinical factors for primary maternal and newborn outcomes. Secondary analyses will further refine predictive models and will evaluate associations of maternal glucose with secondary outcomes and longitudinal modeling of maternal glycemia over the course of pregnancy.

GO MOMs Nutrition Substudy: The GO MOMs Nutrition Study is an observational substudy nested within the GO MOMs parent study. The goal of the study is to describe self-reported dietary components in a diverse cohort of pregnant individuals and to study the relationship between maternal diet and outcomes including maternal glycemia, maternal insulin physiology, infant birth weight, and infant fat mass. Participants will complete 6 dietary recalls via the Automated Self-Administered 24-hour (ASA24) Dietary Assessment Tool during their pregnancies (Figure). Two will occur at visits and four will be unannounced, meaning they are completed on a random day without advance notice, during CGM wear. In addition, stored samples from all GO MOMs participants at visit 1 and 3 will be assayed for other nutritional markers. Primary statistical analyses will be used to identify associations between dietary carbohydrate content at <22 weeks' gestation and maternal glycemia 24-28 weeks' gestation and neonatal birthweight.

Inclusion Criteria:

• Maternal age >=18 at consent
• Singleton gestation
• 10w0d-14w0d gestation at the time of the Visit 1 OGTT and CGM placement according to study dating criteria
• Conceived using own oocyte
• Willing and able to wear CGM as directed and adhere to CGM instructions
• Planning to deliver at GO MOMs-affiliated hospital (see list of accrual sites in the protocol section "Key Roles and Contact Information").

Exclusion Criteria:

• Pre-existing diabetes at enrollment
• Currently self-monitoring blood glucose
• Current use of medication with glycemic effects
• Fetal malformation evident at or before enrollment that is likely lethal. This includes, but is not limited to, malformations such as anencephaly, hydrops, diffuse subcutaneous edema or cystic hygroma, ectopic cordis, and encephalocele
• Known fetal aneuploidy based on chorionic villus sampling
• Participation in other research study that may modify glycemic profile or study outcomes
• History of bariatric surgery
• Extensive skin changes or diseases making CGM sensor use problematic
• Significant allergy to adhesive
• Previous participation in GO MOMs
• Current bulimia or anorexia nervosa
• Overnight shift work that alters the sleep/wake periods
• Hemoglobin A1c >= 6.5%, fasting glucose >= 126 mg/dL or 2 hr glucose >= 200 mg/dL noted during OGTT at 10w0d-14w0d gestation
• Current psychiatric illness/social situation that would limit compliance with study requirements, as determined by the site investigator

Pregnant adults who enroll prior to 10w0d-14w0d gestation.

Participants have the option to agree to share dataset with National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) Repository.