Samimi 2016.

Methods	Prospective, double‐blind, placebo‐controlled trial.
Participants	60 primigravida pregnant women, aged 18–40 years old, who were at risk for pre‐eclampsia, and lived approximately 20 km or less from the clinic and hospital. Women ‘at‐risk’ for pre‐eclampsia were recognised by laboratory tests including free β‐human chorionic gonadotrophin, inhibin a dimeric, unconjugated oestriol and maternal serum α‐foetoprotein, and haemodynamic assessment of uterine artery Doppler wave form at 16 to 20 weeks of gestation.
Interventions	Participants were randomly allocated into 2 groups: Group 1 (n = 30) received 50,000 IU vitamin D3 every 2 weeks plus 1000 mg day 1 calcium supplements (as calcium carbonate); Group 2 (n = 30) received placebos at the same times; from 20 to 32 weeks of gestation. Health worker cadre: an investigator with no clinical involvement in the present study packed cholecalciferol, calcium supplements and placebos into numbered bottles based on the random list. Anthropometric measurements of pregnant women at maternity clinic were measured by a trained midwife at baseline and then after 12 weeks of intervention.
Outcomes	Maternal: serum 25(OH)D concentrations, fasting plasma glucose, serum insulin concentrations, homeostasis model assessment (HOMA)‐B, inQUICKI score, serum HDL‐cholesterol, plasma GSH concentrations, systolic blood pressure, diastolic blood pressure, lipid profiles and inflammatory markers, pre‐eclampsia. Infant: LBW (< 2500 g), newborn’s birth size (newborn’s weight, length and head circumference) and prevalence of preterm delivery (< 37 weeks). Laboratory method used for assessment of vitamin D concentrations: Serum 25‐hydroxyvitamin D concentrations was determined using a commercial enzyme‐linked immunosorbent assay (ELISA) kit (IDS, Boldon, UK) with inter‐ and intra‐assay coefficients of variation (CVs) of 4.5–7.0%, respectively.
Notes	By total dose of supplementary vitamin D during pregnancy: more than 200,000 IU of vitamin D; by start of supplementation: 20 weeks of pregnancy, or more; by pre‐gestational BMI (kg/m2): mixed; by supplementation scheme/regimen: bi weekly; by skin pigmentation based on Fitzpatrick skin tone chart (Fitzpatrick 1988): mixed/unknown; by latitude: north of the Tropic of Cancer; by season at the start of pregnancy: unknown. Source of funding: the study was supported by a research grant from Kashan University of Medical Sciences. Dates of the study and location: September 2014 to February 2015, Kashan, Iran. Declarations of interest among primary researchers (or state where this information is not reported by the trial authors): the authors declare that there are no conflicts of interest.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Parallel, balanced randomisation (1:1).
Allocation concealment (selection bias)	Low risk	Randomisation and allocation were concealed from both researchers and participants until the statistical analysis was completed.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Only the person responsible for the distribution of drugs knew how the women were allocated to the treatment groups.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	The trial reported that it was double‐blinded but they did not specify if those performing the assessments were blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Data were reported for all participants.
Selective reporting (reporting bias)	Unclear risk	There is insufficient information to permit judgement.
Other bias	Low risk	The study appears to be free of other sources of bias.