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Trial name or title	Use of metformin for the prevention of gestational diabetes mellitus in obese pregnant women
Methods	Randomised controlled trial, Joinville, Brazil
Participants	Included: women aged 18 years or more with BMI ≥ 30 kg/m2, singleton pregnancy, between 10 + 0 and 20 weeks of gestation, without gestational diabetes (screened in early pregnancy); or pathology that interferes with glucose metabolism Excluded: women with a contraindication to taking metformin; history or presence of liver disease; gastrointestinal disease or other conditions that interfere with the absorption, distribution, excretion or metabolism of the drug
Interventions	Intervention: women will receive 500 mg metformin orally after breakfast and dinner from 20 weeks of pregnancy until birth; in addition standard monitoring with nutritionist, nurses physiotherapists and obstetricians Control: women will receive standard monitoring with nutritionist, nurses physiotherapists and obstetricians from 20 weeks of pregnancy until birth
Outcomes	Primary outcome: incidence of gestational diabetes Secondary outcome: neonatal hypoglycaemia
Starting date	October 2014
Contact information	William Barbosa Sales; Universidade da Região de Joinville. Phone +55 (41) 8859 9064; email: sallesbio@hotmail.com
Notes

BMI: body mass index