The purpose of this prospective observational study is to establish the performance and safety of the Dexcom G6 CGM System utilized for up to a 10-day wear period in pregnant women with diabetes mellitus.

Primary Study Objective:

To determine the accuracy of Dexcom G6 CGM System glucose readings in reference to arterialized venous sample YSI glucose measurements in pregnant women with diabetes mellitus.

Secondary Study Objective:

To assess the safety of the Dexcom G6 CGM System, through characterization of device-related Adverse Events (AEs), in pregnant women with diabetes mellitus.

Inclusion Criteria:

1. Age ≥ 18 years;
2. Currently in the 2nd or 3rd trimester of pregnancy;
3. Diagnosis of GDM, T1DM, or T2DM;
4. Willing to avoid insulin injections or wear an insulin pump insertion set within 3 inches from the sensor site;
5. Able to follow study procedures;
6. Able to speak, read, and write in English or Spanish.

Exclusion Criteria:

1. Extensive skin changes/diseases that preclude wearing the required number of devices on normal skin (e.g., extensive psoriasis, recent burns or severe sunburn, extensive eczema, extensive scarring, extensive tattoos, dermatitis herpetiformis) at the proposed wear sites;
2. Known allergy to medical-grade adhesives;
3. Hematocrit of < 30%;
4. Prescribed tocolytic drugs for treatment of pre-term labor or experiencing high-risk pregnancy complications, including, but not limited to, pre-eclampsia or HELLP syndrome (hemolysis, elevated liver enzymes, and a low platelet count) during current pregnancy;
5. Currently receiving dialysis treatment or planning to receive dialysis during the sensor wear period;
6. Require a Magnetic Resonance Imaging (MRI) scan, Computed Tomography (CT) scan, or diathermy during the sensor wear period;
7. Current participation in another investigational study protocol (if a subject has recently completed participation in another drug study, the subject must have completed that study at least 30 days prior to being enrolled in this study.);
8. Working for a competitive medical device company or having an immediate family member or person living within the same household who works for such a company (e.g., Medtronic, GlySens Inc., Abbott Laboratories, Roche, Senseonics, Waveform, and Ascencia/POCTech);
9. Any condition that, in the opinion of the Investigator, would interfere with their participation in the trial (e.g., marked visual impairment) or pose excessive risk to study staff handling venous blood samples (e.g., known history of HIV or Hepatitis B or C).

1. Age ≥ 18 years;
2. Currently in the 2nd or 3rd trimester of pregnancy;
3. Diagnosis of GDM, T1DM, or T2DM;