Gestational diabetes mellitus (GDM) is defined as hyperglycemia first-diagnosed during pregnancy. Glycemic control reduces GDM-related complications. With the new diagnostic criteria of GDM, up to 25% of pregnant women have GDM, whereas it was previously 6-10% in France. Therefore caring for women with GDM is very time-consuming. Therapeutic strategy includes dietary and lifestyle measures and additional insulin therapy for 15 to 40% of the women with GDM if the glycemic targets are not achieved after a period of 1 to 2 weeks of diet. Insulin therapy is imperfect for the following main reasons: need for education (i.e. subcutaneous administration, dose titration), hypoglycemia and weight gain, limited acceptance and high cost. Psychosocial deprivation is associated with more cases of GDM and health accessibility may be unequal.

MYO-INOSITOL (MI) is an oral dietary supplement, which reduces insulin resistance. Women with GDM are deficient in MI. MI supplementation safely prevents GDM by 65 to 87% in high-risk women. A pilot study has shown a 75% reduction of the need for insulin during GDM not controlled by diet.

The coordinator investigator propose here, for the first time, a randomized controlled study evaluating MI versus placebo in women with newly diagnosed GDM.

Prospective, multicenter, superiority, randomised, double blind study with two arms.

1. In the 23 participating centers selection of women with GDM between 6 to 37 (+6 days) amenorrhea weeks

2. Explanation of protocol, with signature of consent in case of acceptation.

3. Randomization

   • Experimental group: The women will receive 2 caps of MI with acid folic a day, until delivery
   • Control group: The women will receive 2 caps of placebo (containing only acid folic) a day, until delivery

   In both arms, the participants will be routinely followed up during pregnancy:

   • diet education,
   • self-monitoring of blood glucose before and after meals
   • and during follow-up insulin therapy if glucose value targets are unmet

4. Routine monitoring of the women with GDM in both arms, up to delivery, without use of other oral hypoglycemic agents during pregnancy.

   At delivery:

   • MI (or placebo) will be stopped
   • Events during pregnancy will be collected

5. Last visit three months after delivery. Oral glucose tolerance test, anthropometric measures for women and their child.

Inclusion Criteria:

• Age ≥18 years

• Singleton pregnancy

• GDM diagnosed during pregnancy according to IADPSG (International Association of the Diabetes and Pregnancy Study Groups) criteria, i.e.

  • fasting plasma glucose between 92 mg/dL (5.1 mmol/L) and 125 mg/dL (6.9 mmol/L)
  • and/or 1-hour plasma glucose value after 75 g oral glucose tolerance test (OGTT) ≥ 180 mg/dL (10.0 mmol/L)
  • and/or 2-hour plasma glucose value between 153 mg/dL (8.5 mmol/L) and 199 mg/dL ((11.0 mmol/L)

• or overt diabetes according to 2-hours post OGTT plasma glucose value ≥ 200 mg/dl

• 6 to 37 (+6 days) amenorrhea weeks at the time of randomization

• Capacity for self-monitoring of blood glucose

• Signed informed consent

Exclusion Criteria:

• Insulin use before randomization during this pregnancy
• Use of other oral hypoglycemic agents during this pregnancy
• Long time corticosteroid treatment
• Pre-existing diabetes before pregnancy
• Overt diabetes diagnosed during pregnancy according to fasting plasma glucose ≥ 126 mg/dL (7 mmol/l)
• Lack of Social Insurance
• Insufficient French understanding and speaking
• Participant in another investigational drug study at inclusion visit
• Fetal malformation diagnosed by previous fetal ultrasound
• Personal history of any bariatric surgery
• Hypersensitivity to any ingredient of dietary supplement formulation

The participants in this study are pregnant women with gestational diabetes mellitus.

Double blind