Gestational diabetes mellitus is one of the most frequent complications of pregnancy, that affect between 1 to 14% of population around the world.

There is a few studies to prevent gestational diabetes mellitus in high risk women as Mexican population.

Metformin has been used during pregnancy in women with gestational diabetes and women with polycystic ovary syndrome, with acceptable security for mother and fetus.

Metformin decrease the insulin resistance and weight gain, we believe that metformin may be decrease the risk of gestational diabetes mellitus in high risk women.

Inclusion Criteria:

• Mexican women with pregnancy < 16 weeks of gestation, normal oral glucose tolerance 75g-2h test and 3 or more criteria:

  1. Body mass index > 27 kg/m2
  2. Maternal age >25
  3. History of infertility with polycystic ovary syndrome
  4. History of macrosomic newborn (Weight >4000g)
  5. History of diabetes mellitus in first or second degree.
  6. History of gestational diabetes in previous pregnancy

Exclusion Criteria:

• Any form of pregestational diabetes
• Fasting glucose > 126 mg/dL at first prenatal visit.
• seric creatinine > 1.5 mg/dL
• Hyperthyroidism
• Heart disease
• Hepatic disease
• Renal diseases
• Epilepsy
• Lupus
• Chronic hypertension.