Karamali 2015.

Methods	Randomised, double‐blind placebo‐controlled clinical trial with 2 arms
Participants	Primigravida women, attending a maternity clinic in Arak, Iran, aged 18–40 years old and at risk for pre‐eclampsia. Women were identified as “at‐risk” by abnormal uterine artery Doppler waveform (18–20 weeks’ gestation, mean resistance index > 0.67 or pulsatility index > 1.65 with or without the presence of unilateral or bilateral diastolic notches)
Interventions	Women were randomly divided into 2 groups to receive: ‐ Group 1: 50,000 IU vitamin D supplements (n = 30) ‐ Group 2 (placebo) (n = 30) every 2 weeks from 20 to 32 weeks of gestation. All pregnant women were also taking 400 μg/d folic acid from the start of pregnancy, 60 mg/d ferrous sulphate from the second trimester, and a multivitamin mineral capsule (containing 400 IU vitamin D) from the second half of pregnancy. Health worker cadre: a trained midwife at maternity clinic (Arak,Iran, outside the tropics) did the randomised allocation sequence with a computer random number generator. An investigator with no clinical involvement in the study packed cholecalciferol and placebos in numbered bottles based on the random list. Participants were requested not to alter their regular physical activity or normal dietary intakes throughout the study and not to take any supplements other than the ones provided by the investigators. All pregnant women were also taking 400 μg/d folic acid from the start of pregnancy, 60 mg/d ferrous sulphate from the second trimester, and a multivitamin mineral capsule (containing 400 IU vitamin D) from the second half of pregnancy. Information on pre‐pregnancy weight and BMI were obtained from clinical records. A trained midwife at maternity clinic conducted the anthropometric measurements at the beginning of the study and the end of the intervention.
Outcomes	Maternal Primary Pre‐eclampsia rate Secondary Vitamin D (nmol/L) 32 weeks' gestation Infant Primary Preterm delivery Low birthweight Secondary Birthweight and length Head circumference Laboratory method used for assessment of vitamin D concentrations: Serum 25‐hydroxyvitamin D concentrations was assayed by a commercial ELISA kit (IDS, Boldon, UK). The inter‐ and intra‐assay CVs for serum 25‐hydroxyvitamin D assays ranged from 4.9 to 7.2%
Notes	• Start of supplementation: from 20 weeks of pregnancy • Pre‐gestational BMI (kg/m2): the Intervention was stratified by BMI (< 25 and ≥ 25 kg/m2) • Supplementation scheme/regimen: UI every 2 weeks • Skin pigmentation based on Fitzpatrick skin tone chart (Fitzpatrick 1988): not applicable • Latitude: outside the Tropics • Season at the start of pregnancy: summer? Source of funding: this trial was supported by a grant from the Vice‐chancellor for Research, AUMS, and Iran. The study was supported by a grant (no. 92–12–161) from Arak University of Medical Sciences Dates of the study: July 2014 and October 2014 Declarations of interest among primary researchers: the authors declare no conflict of interest
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomised allocation sequence by a computer random number generator.
Allocation concealment (selection bias)	Low risk	An investigator with no clinical involvement in the study packed cholecalciferol and placebos in numbered bottles based on the random list.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Randomisation and allocation were hidden from the researchers and pregnant women until the statistical analysis was completed.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Randomisation and allocation were hidden from the researchers and pregnant women until the statistical analysis was completed.
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants completed the study (G1: n = 30, G2: 30); data for both groups were reported.
Selective reporting (reporting bias)	Low risk	According to the methodology, all outcomes data were reported.
Other bias	Low risk	No other bias source was identified.