Asemi 2013a.

Methods	Randomised, double‐blind, placebo‐controlled clinical trial with 2 arms: vitamin D and placebo, during March 2012 to September 2012.
Participants	48 healthy pregnant women, primigravida, aged 18–40 years old at 25 weeks of gestation and a singleton pregnancy attending maternity clinics affiliated with Kashan University of Medical Sciences, Kashan, Islamic Republic of Iran. Women with pre‐eclampsia, hypertension, GDM, IUFD, or those with a history of rheumatoid arthritis, hepatic or renal failure, metabolic bone disease and malabsorption, or thyroid, parathyroid, or adrenal diseases were excluded from the analysis. Also, smokers and those taking medications including nonsteroidal antiinflammatory drugs and aspirin were excluded.
Interventions	Participants were randomly assigned to receive 1 of 2 groups: group 1 (n = 24) received 400 IU vitamin D (cholecalciferol‐D3) supplements daily; and group 2 (n = 24) received placebo for 9 weeks. Additionally, all participants also consumed 400 mcg (0.4 mg) folic acid daily from the beginning of pregnancy and 60 mg elemental iron (as ferrous sulphate) daily from the second trimester. Health worker cadre: the trial was carried out in maternity clinics affiliated to Kashan University of Medical Sciences, Kashan, Islamic Republic of Iran and the investigators provided the supplements to the participants. A trained midwife at the maternity clinic performed anthropometric measurements at study baseline and at 6 weeks after the intervention.
Outcomes	Maternal: weight, height, BMI, systolic blood pressure and diastolic blood pressure, serum calcium concentrations, serum 25‐hydroxyvitamin D [25(OH)D], serum hs‐C‐reactive protein, fasting plasma glucose, serum cholesterol, LDL‐cholesterol, HDL‐cholesterol concentrations, serum insulin, quantitative Insulin sensitivity check index (QUICKI) score, plasma total antioxidant capacity, plasma total glutathione, GDM, preterm delivery, IUFD, placental abruption, severe pre‐eclampsia. Laboratory method used for assessment of vitamin D concentrations: serum 25‐hydroxyvitamin D concentrations were measured using a commercial ELISA kit (Immuno Diagnostic Systems).
Notes	Total dose of supplementary vitamin D during pregnancy: 56,000 IU vitamin D or less; start of supplementation: 20 weeks of pregnancy or more; pre‐gestational BMI (kg/m2): overweight (25 or higher); supplementation scheme/regimen: daily in a 9‐week period; skin pigmentation based on Fitzpatrick skin tone chart (Fitzpatrick 1988): mixed/unknown; latitude: north of the Tropic of Cancer; season at the start of pregnancy: spring‐summer period. Source of funding: study was funded by research grant from the Vice‐chancellor for Research, Kashan University of Medical Sciences, Kashan, Iran. Dates of the study and location: March 2012 to September 2012, Kashan, Iran. Declarations of interest among primary researchers (or state where this information is not reported by the trial authors): there are no conflicts of interest.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Random assignment was performed by the use of computer‐generated random numbers.
Allocation concealment (selection bias)	Low risk	A trained midwife at the maternity clinic performed the randomised allocation sequence and assigned participants to the groups. Placebo pills contained microcrystalline cellulose and were packed in identical tablets and coded by the producer to guarantee blinding.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Participants and investigators were blind to the interventions.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Measurements of laboratory were performed in a blinded fashion, in duplicate, in pairs (before/after intervention) at the same time, in the same analytical run, and in random order to reduce systematic error and inter assay variability.
Incomplete outcome data (attrition bias) All outcomes	Low risk	3 in each group were lost to follow‐up.
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.