Grant 2013.

Methods	Randomised, double‐blind, placebo‐controlled multi‐arm parallel study.
Participants	260 pregnant women 26 to 30 weeks' gestation, with a singleton pregnancy attending community based primary care maternity clinic in Auckland, New Zealand (latitude 36°S) from April 2010 to July 2011 and then their infants, from birth to age 6 months. Women already taking vitamin D supplementation 200 IU per day, a history of renal stones or hypercalcaemia, or any serious pregnancy complication at enrolment were excluded from the study.
Interventions	Participants were randomly assigned to 1 of 3 mother/infant groups: group 1 (n = 87) women received placebo from 26 to 30 weeks of pregnancy until parturition and their infants also received placebo from 0‐6 months of age; group 2 (n = 87) women received 1000 IU vitamin D (cholecalciferol‐D3) from 26 to 30 weeks of pregnancy until parturition and their infants received 400 IU vitamin D from 0 to 6 moths of age; group 3 (n = 86) women received 2000 IU vitamin D (cholecalciferol‐D3) from 26 to 30 weeks of pregnancy until parturition and their infants received 800 IU from birth to 6 months of age. Data from groups 2 and 3 were combined for our analysis. Health worker cadre: the study was conducted by the research team but it is not reported who provided the supplements or measured the outcomes.
Outcomes	Maternal: serum 25(OH)D concentration. Infant: serum 25(OH)D concentration. Laboratory method used for assessment of vitamin D concentrations: serum 25‐hydroxyvitamin D concentration was measured using isotope‐dilution liquid chromatography–tandem mass spectrometry in a Vitamin D External Quality Assurance Scheme–certified laboratory.
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): unknown/mixed; supplementation scheme/regimen: daily; skin pigmentation based on Fitzpatrick skin tone chart (Fitzpatrick 1988): mixed/unknown; latitude:between Tropics of Cancer and Capricorn; season at the start of pregnancy: all year round. Source of funding: Health Research Council of New Zealand, grant number 09/215R. Dr Mitchell is supported by Cure Kids. Study medicine was prepared by the Ddrops Company (Woodbridge, Ontario, Canada). This study was funded by a combination of government programmes and non‐governmental organisations (NGOs). Dates of the study and location: April 2010 to July 2011, Auckland, New Zealand. Declarations of interest among primary researchers (or state where this information is not reported by the trial authors): the authors have indicated they have no potential conflicts of interest to disclose.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Trial reported computer‐generated randomisation list.
Allocation concealment (selection bias)	Low risk	The allocation sequence was concealed from research staff involved in recruitment. Trial reported randomly allocated treatment to each participant and labelled identical study medicine bottles such that study staff and participants were unaware of the treatment status.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	The study statistician randomly allocated a treatment to each participant and labelled identical study medicine bottles such that study staff and participants were unaware of the treatment status.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	The study staff and participants were unaware of the treatment status.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Reported compliance did not differ between groups. In the placebo group, 6 did not complete the study; in the lower dose vitamin D group, 6 did not complete the study. In the higher vitamin D dose group, 6 did not complete the study.
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.