Mallet 1986.

Methods	Randomised controlled trial; 3‐arm design with individual randomisation.
Participants	77 white pregnant women 18 to 36 years of age in the last trimester of pregnancy living in Northwest of France (latitude: 49° 26' 0" N north of Tropic of Cancer). Pre‐gestational BMI not reported.
Interventions	Participants were randomly assigned to 1 of 3 groups: group 1 (n = 21) women received daily 1000 IU of vitamin D (ergocalciferol‐D2) for the last 3 months of pregnancy (estimated total dose throughout pregnancy: 90,000 IU); group 2 (n = 27) women received a single dose of 200,000 IU (5 mg) vitamin D at the 7th month of pregnancy; group 3 (n = 29) women received no supplement and served as controls. Length of the intervention/follow‐up: 12 weeks from start of supplementation to term. Health worker cadre: the study was conducted by the research team at the maternity of Balvedere, Rouen, France but the roles are not described. It is unclear who provided the supplements and measured the outcomes.
Outcomes	Maternal: 24‐hour urinary calcium excretion after 6 weeks supplementation, calcium, 25‐hydroxyvitamin D (25‐OHD) and1‐alfa,25‐dihydroxyvitamin D (1,25(OH)2D) metabolites of vitamin D from serum and cord during labour and delivery. Infant: serum calcium levels at days 2 and 6 of life, birthweight. Laboratory method used for assessment of vitamin D concentrations: for 25‐hydroxyvitamin D and 1,25‐dihydroxyvitamin D determinations the following techniques were used: extraction with chloroform‐methanol‐water according to Preece, double step purification, first on a Sephadex LH 20 column with chloroform hexan 45 to 55 vol/vol as solvent, then on a high‐pressure liquid pression system according to Shepard. Plasma metabolites were measured by competitive assay using rat protein for 25 OHD and chicken intestine cytosol for 1,25 (OH)2 D according to Jongen. Assay sensitivity for 1,25 (OH)2 D was 5 pmol/tube and for 25 OHD was 25 pmol/tube.
Notes	Total dose of supplementary vitamin D during pregnancy: more than 56,000 to 200,000 IU; start of supplementation: 20 weeks of pregnancy or more; pre‐gestational BMI (kg/m2): unknown/mixed; supplementation scheme/regimen: single/daily; skin pigmentation based on Fitzpatrick skin tone chart (Fitzpatrick 1988): unknown/mixed; latitude: north of the Tropic of Cancer; season at the start of pregnancy: winter pregnancy. Infants born during February and March. Source of funding: unknown/unreported. Dates of the study and location: January 1979 to December 1982, France. 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	Randomisation was conducted by random numbers table.
Allocation concealment (selection bias)	Unclear risk	The trial did not report the method of concealment. It is assumed that it was not conceal 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 it 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 it was blinded.
Incomplete outcome data (attrition bias) All outcomes	High risk	It is unclear if there was attrition, but given the uneven number of participants reported, it is likely that there were losses to follow‐up.
Selective reporting (reporting bias)	Unclear risk	There is insufficient information to permit judgement.
Other bias	High risk	Groups are reported with notorious different sample sizes. It is unclear whether the numbers reflect the participants who finished the trial (unclear and uneven losses to follow‐up); a non randomised process; or a selection bias in which randomised participants did not receive the intervention.