Asemi 2012.

Methods	RCT described as single‐blind controlled clinical trial Individual randomisation
Participants	Setting: maternity clinics in Kashan Iran. Dates of recruitment: April 2011 to February 2012. Inclusion criteria: pregnant nulliparous women at risk of pre‐eclampsia, singleton pregnancy, 18‐35 years in third trimester. High risk was defined as nulliparous, with environmental, socioeconomic factors or obesity (not clear). 54 women recruited. Exclusion criteria: women with severe pre‐eclampsia, intrauterine fetal death, placental abruption, preterm birth or GDM.
Interventions	Experimental intervention: calcium‐vitamin D supplements for 9 weeks (500 mg calcium carbonate plus 200 IU vitamin D per day). Total number randomised: n = 27 women (24 analysed). Control/comparison intervention: placebo. Total number randomised: n = 27 women (25 analysed).
Outcomes	Compliance monitored weekly. Dietary intake (from diaries). Maternal weight, BMI, blood biochemical outcomes (fasting plasma glucose, cholesterol, high and low density lipoprotein‐cholesterol).
Notes	Funding: the study was supported from a grant (university or government). Grant from the Vice‐chancellor for Research, Kashan University of Medical Sciences (KUMS). Study placebo provided by Share Darou Co, Tehran, Iran and supplements by Darou Pakhsh Co. CoI: not stated.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The method of sequence generation was not described.
Allocation concealment (selection bias)	Unclear risk	This was a placebo controlled study but it was not clear how women were assigned to groups. Although the supplements and placebo packs were described as identical it was not clear whether or not staff were aware of allocation.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Described as a single‐blind trial. It was not clear what this meant. Women were provided with active or placebo drugs in identical packs. Only participants were blinded.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	It was not clear if outcome assessment was blind but as most outcomes were biochemical lack of blinding may not have impacted on outcomes.
Incomplete outcome data (attrition bias) All outcomes	High risk	54 women were recruited, 49 included in the analyses (25 in placebo group, 24 in calcium/vitamin D group). Women with severe pre‐eclampsia, preterm birth and GDM were excluded — it was not clear if these exclusions were after randomisation — these outcomes may have related to the intervention.
Selective reporting (reporting bias)	Unclear risk	We did not have access to the study protocol. It was not clear if all outcome data collected was reported.
Other bias	Unclear risk	Women in the placebo group had slightly lower weights pre‐pregnancy (and throughout pregnancy).