D'Anna 2013.

Study characteristics
Methods	Study type: parallel RCT
Participants	220 women from Italy Inclusion criteria: first‐degree relative (mother, father or both) affected by type 2 diabetes, pre‐pregnancy BMI < 30 kg/m2, fasting plasma glucose < 126 mg/dL and random glycaemia < 200 mg/dL, singleton pregnancy, Caucasian. Women were 12 to 13 weeks' gestation at study entry. Exclusion criteria: pre‐pregnancy BMI ≥ 30 kg/m2, previous gestational diabetes, pre‐gestational diabetes, first trimester glycosuria, first‐degree relative (mother or father) not affected by type 2 diabetes, fasting plasma glucose ≥ 126 mg/dL or random glycaemia ≥ 200 mg/dL, twin pregnancy, associated therapy with corticosteroids, PCOS. Location: Department of Gynecology and Obstetrics, University of Messina, Messina, Italy Timeframe: 2010 to 2012
Interventions	Intervention: 4 g myo‐inositol plus 400 mcg folic acid daily (2 g myo‐inositol plus 200 mcg folic acid twice a day) (N = 110) Duration of myo‐inositol supplementation: from trial entry until the end of pregnancy Comparison: 400 mcg folic acid daily (200 mcg folic acid twice a day) as placebo (N = 110)
Outcomes	Maternal: incidence of gestational diabetes, gestational hypertension, caesarean section Criteria used to diagnose gestational diabetes: IADPSG Infant: fetal macrosomia (> 4000 g), preterm birth, shoulder dystocia, neonatal hypoglycaemia, respiratory distress syndrome
Notes	Sample size calculation: not stated Intention‐to‐treat analysis: yes (carried out but not reported) Losses to follow‐up: 11 women in the intervention group and 12 in the comparison group Funding source: none, the women bought the supplement on their own Conflict of interest: none reported Further information was received following email contact with the authors.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Computer randomization was used"
Allocation concealment (selection bias)	Unclear risk	Method of allocation concealment not stated
Blinding of participants and personnel (performance bias) All outcomes	High risk	Open‐label trial. Blinding not carried out
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Primary outcome of incidence of gestational diabetes diagnosed by blood test so blinding unlikely to impact assessment of this outcome. However, other secondary outcomes are more subjective.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Overall 10% loss to follow‐up
Selective reporting (reporting bias)	Low risk	All pre‐specified outcome measures were reported.
Other bias	Low risk	Intention‐to‐treat analysis was carried out on the available data.