Myo-inositol has been shown to decrease the rate of diabetes in pregnancy in European studies. It is not known exactly how this occurs or what it does to the sugar when the supplement is taken. This study purpose is to look at the patient's sugar levels while taking the supplement to see if the overall levels of sugar go down. We hypothesize that in addition to sugar levels, other hormones influencing diabetes will be altered.

Myo-inositol is important for glucose homeostasis and has been shown to improve insulin sensitivity. This is a prospective cohort pilot study to determine daily glycemic pharmacokinetics and metabolic influences of myo-inositol supplementation using continuous glucose monitoring system (CGMS) and pre- and post-supplement blood work in high risk pregnancies and women diagnosed with gestational diabetes mellitis (GDM). Risk factors include: obesity, previous pregnancy with GDM, family history of diabetes, glucose intolerance, and polycystic ovarian syndrome (PCOS). Women will have a CGMS device placed on day one and begin with 3 days of placebo plus folic acid (400mcg) to determine baseline glycemia and metabolic levels. For the final 4 days, women with take myo-inositol supplementation (4g) plus folic acid (400mcg). The CGMS device will be removed on day 7 when final blood work will be obtained. Self-capillary glucose testing 4 times per day is recorded to calibrate CGMS glucose values. These observations will help determine the effects of myo-inositol on overall mean glucose and other metabolic factors in high risk and GDM patients, identify pharmacokinetic discipline in pregnancy, and develop the groundwork for future prospective clinical trials for the prevention and/or augmentation in treatment GDM.

Inclusion Criteria:

• English-speaking
• singleton
• pregnant females between 20-28 weeks of gestation at time of enrollment PLUS (either of the following)
• High risk including women must have passed routine glucose screening and have greater than or equal to 1 of the following high risk criteria: first degree family member with diabetes mellitus, previous pregnancy with gestational diabetes, PCOS, or body mass index great than or equal to 30.
• Gestational diabetes diagnosed in current pregnancy based on IADPSG or NIH consensus diagnostic recommendation

Exclusion Criteria:

• pre-pregnancy diagnosis of diabetes mellitus
• renal disease
• immunocompromised
• currently taking immunosuppressive medications
• age <13 years old
• non-English speaking
• multifetal gestation.