Table I.

Shows a summary of the design and main findings of included studies

Study ID	Study design			Intervention group	Population	Sample size		Main findings
	Design	Crossover or parallel	Blinding			Initial	ITT
Syngelaki 2015	Randomized, placebo-controlled trial	Parallel	Double blinded	Metformin 500-2500 mg/day	- Pregnant women aged ≥16 yr - between 12 and 16 wk gestation - BMI of 30 kg/m2 or more - Normal glucose tolerance	449	443	Both groups were comparable in terms of median birth weight Z score, maternal weight gain and adverse events.
Chiswick 2016	Randomized, placebo-controlled trial	Parallel	Double blinded	Metformin 3 grams/day		450	400	Metformin reduced maternal weight gain; however, there were no significant differences in birth weight Z score or birth consequences.