Marya 1988.

Methods	Randomised clinical trial; 2‐arm design with individual randomisation.
Participants	200 pregnant women, aged 22 to 35 years old, attending the antenatal clinic of the Medical College Hospital, Rohtak, India (latitude: 76° 34' 0' north of Tropic of Cancer). Inclusion criterion: uncomplicated single pregnancy. Exclusion criteria: pre‐eclampsia, antepartum haemorrhage, premature delivery. Pre‐gestational BMI and skin pigmentation not reported.
Interventions	Participants were allocated to 1 of the following groups: group 1 (n = 100) women received 2 doses of 600,000 IU (each dose at 7th and 8th month of pregnancy (estimated total dose: 1,200,000 IU); group 2 (n = 100) women received no intervention and served as controls. Length of the intervention/follow‐up: 12 weeks from start of supplementation to term. Health worker cadre: not specified.
Outcomes	Maternal: venous and cord serum calcium, serum proteins, inorganic phosphate, alkaline phosphatase, weight. Radiological examination on women with abnormal biochemistry or osteomalacia symptomatology. Side effects: back age, leg‐pains, general weakness, cramps. Infant: birthweight, LBW, crown‐heel length, head circumference, mid‐arm circumference within 24 hours after birth. Skinfold thickness (triceps and infrascapular). Laboratory method used for assessment of vitamin D concentrations: not applicable.
Notes	Total dose of supplementary vitamin D during pregnancy: more than 200,000 IU of vitamin D; start of supplementation: 20 weeks of pregnancy or more; pre‐gestational BMI (kg/m2): unknown/mixed; supplementation scheme/regimen: 2 single doses were provided at 7th and 8th month of pregnancy; 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: mixed/unknown. Source of funding: unknown/unreported. Dates of the study and location: not reported dates, India. 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)	Unclear risk	The trial reported that participants were randomly allocated to the intervention groups but they did not report the method of sequence generation.
Allocation concealment (selection bias)	Unclear risk	The trial did not report the method of concealment. It is assumed that they did not conceal the allocation as one of the groups did not receive any supplementation.
Blinding of participants and personnel (performance bias) All outcomes	High risk	The trial did not report if the study was blinded. It is assumed that it was not blinded to participants as one of the groups did not receive any supplementation.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	The trial did not report if the research staff was blinded.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Losses to follow‐up are not documented although exclusions included pregnancy complications. Results tables mention that each arm was comprised of 100 women, a number that corresponds to that described for the treatment allocation.
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.