Purwar 1996.

Methods	Type of study: randomised double‐blind placebo‐controlled trial. Method of treatment allocation: the women were assigned randomly in a double‐blind fashion to 1 of 2 treatment groups (calcium/placebo) using computer‐generated random number table. All the containers and tablets were specially prepared by local Universal pharmaceutical, Nagpur. Stratification: not stated. Placebo: yes, starch tablets. Sample size calculation: not stated. Intention‐to‐treat analyses: no. Losses to follow‐up: yes, 11 in 201 = 5.5%.
Participants	Location: the Government Medical College and Hospital, Nagpur, India. Time frame: October 1,1993 to December 31, 1994. Eligible criteria: nulliparity, normal single viable pregnancy with known menstrual period date (LMP), registering at antenatal clinic before 20 weeks of gestation and intending to undergo delivery at the same institution, normal glucose tolerance test < 140 mg/dl and willing to participate in trial, first antenatal visit below 140/90 mmHg and free of any underlying medical disorders, based on a comprehensive medical examination and routine laboratory tests.   Exclusion criteria: renal disease, collagen vascular disease, chronic hypertension, endocrinological disease or if on any medication. Total recruited: 201 pregnant women; treatment group, n = 103, control group, n = 98. Final number for analysis (treatment group n = 97, control group n = 93).
Interventions	2 g calcium (4 tablets of 500 mg calcium carbonate). Placebo (4 tablets of placebo) same size, weight and colour.
Outcomes	Incidence of PIH. Pregnancy outcomes; preterm birth, birthweight, fetal growth restriction.
Notes	Missing data 11 in 201 = 5.5%.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "The women were assigned randomly in a double‐blind fashion at 20 weeks gestation to 1 of 2 treatment groups (calcium/placebo) using computer‐generated random number table."
Allocation concealment (selection bias)	Low risk	Quote: "All the containers and tablets used were specially prepared for the study by local Universal Pharmaceutical Pvt Ltd, Nagpur."
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "The calcium supplemented group received 4 tablets of calcium (500 mg of elemental calcium each) for total 2 g and the placebo group received 4 tablets of the same size, weight, and colour."
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "Blood pressure were measured by one physician specially trained. Any ante/intrapartum maternal and fetal complications were recorded."
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "A total of 98 women randomly assigned to the placebo groups and 103 in calcium groups. Eleven women (5.47%) were lost to follow‐up after randomisation (5 in the placebo group and 6 in the calcium group). The total of 93 women in the placebo group and 98 women in the calcium group were included in the fin final analysis." Missing data 11 in 201 = 5.5%.
Selective reporting (reporting bias)	Unclear risk	None identified. There were inconsistent missing data. The number lost to follow‐up is 11 from 201; t200 participants should have remained in the final analysis, but the given number included in final analysis was 201 participants.
Other bias	Low risk	None identified.