Roth 2013.

Methods	Randomised, double‐blind, placebo‐controlled trial (MDIG trial).
Participants	1300 generally‐healthy pregnant women between 17 and 24 weeks of gestation.
Interventions	Participants were randomly assigned at enrolment to 1 of 5 groups: group 1 (n = 260) received placebo throughout the prenatal period and for 26 weeks postpartum; group 2 (n = 260) received 4200 IU per week prenatally and no supplementation postpartum; group 3 (n = 260) received 16,800 IU per week prenatally and no supplementation postpartum; group 4 (n = 260) received 28,000 IU per week prenatally and no supplementation postpartum; and group 5 (n = 260) received 28,000 IU per week prenatally and during the postpartum for 26 weeks. Data from groups 2‐5 were combined into the intervention group for this analysis. All participants received calcium (500 mg per day), iron (66 mg per day), and folic acid (350 mcg per day) throughout the intervention phase. Health worker cadre: trial personnel contacted participants weekly from enrolment until 26 weeks postpartum, and infants were further assessed at 9 months and 12 months of age. Visits were conducted in the home or at a clinic and included the use of standardized questionnaires, point‐of‐care tests, anthropometric measurements, and specimen collection.
Outcomes	Maternal: maternal serum 25‐hydroxyvitamin D and calcium concentration, urinary calcium excretion, and maternal PTH concentrations. Infant: length‐for‐age, birth outcomes, morbidity and serum 25‐hydroxyvitamin D and calcium concentrations. Laboratory method used for assessment of vitamin D concentrations: point‐of‐care tests.
Notes	Total dose of supplementary vitamin D during pregnancy: more than 56,000 IU; start of supplementation: 17‐24 weeks of pregnancy; pre‐gestational BMI (kg/m2): unknown/mixed; supplementation scheme/regimen: weekly; 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: unknown. Source of funding: this study was funded by the Bill & Melinda Gates Foundation. Dates of the study and location: March 2014 to September 2015, Dhaka, Bangladesh. Declarations of interest among primary researchers (or state where this information is not reported by the trial authors): no potential conflict of interest was reported.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation was conducted by computer‐generated, simple randomisation scheme created independently by the trial statistician.
Allocation concealment (selection bias)	Low risk	Concealment of trial‐group assignments was ensured with the use of pre‐labelled and sequentially numbered but otherwise identical supplement vials.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	The trial reported that a master list linking participants to supplementation groups was not accessible to trial personnel until final group assignments were revealed.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	The trial reported that a master list linking participants to supplementation groups was not accessible to trial personnel until final group assignments were revealed.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Among 1164 infants assessed at 1 year of age (89.5% of 1300 pregnancies), < 5% of participants withdrew or were excluded after randomisation until birth.
Selective reporting (reporting bias)	Unclear risk	There is insufficient information to permit judgement.
Other bias	Low risk	There is no any evidence of other bias.