Longitudinal Observation of Insulin Requirements and Sensor Use in Pregnancy

Inclusion Criteria: * Clinical diagnosis, based on investigator assessment, of T1D for at least one year and using insulin for at least 1 year. * Criteria for documented hyperglycemia (at least 1 must be met): * Fasting glucose ≥126 mg/dL * Two-hour OGTT glucose ≥200 mg/dL * HbA1c ≥6.5% documented * Random glucose ≥200 mg/dL with symptoms * No data at diagnosis is available but the participant has a convincing history of hyperglycemia consistent with T1D * Criteria for requiring insulin at diagnosis (1 must be met): * Participant required insulin at diagnosis and continually thereafter. * Participant did not start insulin at diagnosis but upon investigator review likely needed insulin (significant hyperglycemia that did not respond to oral agents) and did require insulin eventually and used continually. * Participant did not start insulin at diagnosis but continued to be hyperglycemic, had positive islet cell antibodies - consistent with latent autoimmune diabetes in adults (LADA) and did require insulin eventually and used continually. * Currently using an insulin pump for diabetes management * Currently using or willing to use an insulin-to-carbohydrate ratio to calculate meal bolus sizes * Willing to change insulin infusion site at least every 3 days. * Confirmed pregnancy * Current gestational age \<17 weeks * Age 18-40 years * HbA1c \<10.0% * Demonstration of proper mental status and cognition for the study * Ability to access the internet and upload CGM data remotely if needed * An understanding of and willingness to follow the protocol and sign the informed consent Exclusion Criteria: * 670 G users in Auto mode * Current gestational age ≥17 weeks * Cystic fibrosis * A known medical condition that in the judgment of the investigator might interfere with the completion of the protocol such as the following examples: * Inpatient psychiatric treatment in the past 6 months * Abnormal renal function test results (calculated GFR \<60 mL/min/1.73m2); testing required for subjects with diabetes duration of greater than 5 years post onset of puberty * Active gastroparesis * Abuse of alcohol or recreational drugs * Infectious process not anticipated to resolve prior to study procedures (e.g. meningitis, pneumonia, osteomyelitis) * Uncontrolled arterial hypertension (Resting diastolic blood pressure \>95mmHg and/or systolic blood pressure \>160 mmHg) at the time of screening * Chronic oral steroid use * A recent injury to body or limb, muscular disorder, use of any medication, any carcinogenic disease, or other significant medical disorder if that injury, medication or disease in the judgment of the investigator will affect the completion of the protocol