Bhutta 2011.

Methods	Randomised, parallel assignment, double‐blind trial.
Participants	115 pregnant females from 12 to 20 weeks of gestation who agreed to participate in the study with presence of at least 20 natural teeth in mouth excluding third molars. For controls: non pregnant, healthy females matched with pregnant women with respect to age and education. Exclusion criteria: pregnant females with high vitamin D levels, women with metabolic diseases such as diabetes (type 1 or 2), presence of acute dental or periodontal disease, presence of systemic disease and/or medication affecting the periodontium; receipt of systemic antibiotic treatment or dental prophylaxis in the previous 3 months and those who do not provide informed consent.
Interventions	Participants were individually randomised to 1 of 2 groups: group 1 (n = 36): vitamin D3 4000 mg per day (given as 1 tablespoon syrup per day); and group 2 n = (49): placebo (given as 1 table spoon syrup per day,) for approximately 6 months. Health worker cadre: CHWs were responsible for the delivery of supplementation to the study participants. The CHWs were assigned to visit study participants, on a fortnightly basis. The first supplementation was provided by the physician at the time of recruitment; later on, the CHWs continued to replenish the supply fortnightly.
Outcomes	Maternal: Periodontal Probing Depth, Interleukin 6 (IL‐6), IL‐2, IL‐4, IL‐10, TNF, IFN‐ɣ and IL‐17 levels. Laboratory method used for assessment of vitamin D concentrations: vitamin D levels were analysed on DiaSorin‐LIASON Inc, kit.
Notes	Total dose of supplementary vitamin D during pregnancy: more than 200,000 IU; start of supplementation: 12 to 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: north of the Tropic of Cancer; season at the start of pregnancy: unknown. Source of funding: the study was supported with a research grant from Pakistan Initiative for Mothers and Newborns (PAIMAN). Dates of the study and location: launched in 2004, Jhelum, Pakistan. Declarations of interest among primary researchers (or state where this information is not reported by the trial authors): none declared.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	The study participants were randomised in blocks.
Allocation concealment (selection bias)	Low risk	Allocation codes for vitamin D and placebo were kept in a sealed envelope in a locked cabinet at the Aga Khan University until the completion of the study.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	The investigators, study staff, and the participants were blinded about the group allocation.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Allocation codes for vitamin D and placebo were kept in a sealed envelope in a locked cabinet at the Aga Khan University until the completion of the study.
Incomplete outcome data (attrition bias) All outcomes	High risk	Only recorded birthweight from 63/85 (74.1%) 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.