Delvin 1986.

Methods	Randomised trial; 2‐arm design with individual randomisation.
Participants	40 pregnant women attending their compulsory visit during the third month of pregnancy at the Obstetrical Unit of the Hopital Edouard Herriot, Lyon, France (latitude: 45° 45' 0" N north of Tropic of Cancer). Inclusion criterion: singleton pregnancy at term and uneventful vaginal deliveries. Pre‐gestational BMI and skin pigmentation not reported.
Interventions	Participants were randomly assigned to 1 of 2 groups at the time of the compulsory visit: group 1 (n = 20): women received daily 1000 IU vitamin D (cholecalciferol‐D3) (estimated total dose: 55,000 IU) and group 2 (n = 20): women received no supplement, during the last trimester of pregnancy for 12 weeks from start of supplementation to term. Health worker cadre: compliance was verified by a weekly visit by a midwife.
Outcomes	Maternal: serum (during last trimester of pregnancy) and cord blood immunoreactive PTH, 25‐hydroxyvitamin D (25‐OHD), 1‐alfa,25‐dihydroxyvitamin D (1,25(OH)2D), total calcium, ionised calcium, magnesium, inorganic phosphate. Infant: immunoreactive PTH, 25‐hydroxyvitamin D (25‐OHD), 1‐alfa,25‐dihydroxyvitamin D (1,25(OH)2D), total calcium, ionised calcium, magnesium, inorganic phosphate at 4 days of age. Laboratory method used for assessment of vitamin D concentrations: Serum 25‐hydroxyvitamin D and 1,25‐dihydroxyvitamin D levels were measured by radioligand assays with slight modifications. With sample volumes of 0.75 mL to 1.5 mL, the inter assay variation coefficient for the 2 assays were 8% and 10%, respectively.
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: north of the Tropic of Cancer; season at the start of pregnancy: winter‐spring. All selections were performed in December, and all deliveries occurred in June. Source of funding: Shriners of North America, the France‐Quebec Exchange Program, and INSERM Grant 121023. This study was funded by a combination of research grant and non governmental organisations. Dates of the study and location: not reported dates, Lyon, 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)	Unclear risk	Trial reported as randomised but the method of sequence generation was not described.
Allocation concealment (selection bias)	Unclear risk	The method of concealment was not described.
Blinding of participants and personnel (performance bias) All outcomes	High risk	The trial reported that women were assigned, by a blind randomisation process, to 1 of 2 groups at the compulsory visit in the third month of pregnancy. 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	There is insufficient information to permit judgement.
Incomplete outcome data (attrition bias) All outcomes	High risk	1 participant from the control group (5%) and 5 (25%) from the vitamin D supplemented group were lost. Laboratory methods reported for 25 to 30 participants (depending on the outcome) out of 40 originally randomised.
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.