Marya 1987.

Methods	Randomised controlled trial; 2‐arm design with randomisation at individual level.
Participants	400 pregnant women 20 to 35 years of age, attending the antenatal clinic of Medical College Hospital in Rohtak, India (latitude: 76° 34' 0' north of Tropic of Cancer). Pre‐gestational BMI and skin pigmentation not reported.
Interventions	Participants were allocated to 1 of 2 groups: group 1 (n = 200) received a daily supplement containing 1200 IU vitamin D and 375 mg calcium (estimated total dose from week 20 to 24 of gestation to term:134,400‐168,000 IU); group 2 (n = 200) received no supplement from 20 to 24 weeks of pregnancy until delivery and served as controls. Length of the intervention/follow‐up: 20 to 24 weeks from start of supplementation to term. Health worker cadre: not specified.
Outcomes	Maternal: pre‐eclampsia (defined as blood pressure of 140 mmHg or higher systolic and/or 90 mmHg diastolic along with proteinuria higher than 300 mg/24 hours); systolic and diastolic blood pressure at 24, 28, 32 and 36 weeks of gestation. Serum calcium and creatinine. Laboratory method used for assessment of vitamin D concentrations: not applicable.
Notes	Biochemical analyses were made for those who developed pre‐eclampsia (n = 12) and also in a group of women with no pre‐eclampsia (n = 25) and a control group of non pregnant women. The results of the stratified analysis are not reported in this review. 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: 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: 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	High risk	Only data on biochemical were reported for those who developed pre‐eclampsia and some of those with no pre‐eclampsia and a group of non pregnant controls.
Selective reporting (reporting bias)	High risk	Outcomes reported for some subgroups only.
Other bias	Low risk	The study appears to be free of other sources of bias.