Rogers 1999.

Methods	Type of study: randomised trial. Method of treatment allocation: unsealed envelopes. Stratification: not stated. Placebo: no (no treatment). Sample size calculation: not stated. Intention‐to‐treat analyses: yes. Losses to follow‐up: 18 in 237 =7.6%.
Participants	Location: Chinese Women's Hospital, Hong Kong. Time frame: July 1992 to December 1994. Eligible criteria: normotensive, MAP > 80 and < 106 mmHg, second trimester, singleton and used cutoff value 60 mmHg of left lateral position. Exclusion criteria: MAP < 60 mmHg. Total recruited: 500 pregnant women (131 patients were excluded only 369 patients were randomised),154 in calcium group, 132 in low‐dose aspirin, 83 in control group.
Interventions	Compared 3 groups of total 369 patients. Calcium (154 patients) 600 mg/day from 22 to 32 weeks and 1200 mg/d in dividing dose from 32 weeks to delivery. Low dose aspirin (132 patients) 80 mg/d starting at 22 weeks until delivery. Control group were no treatment in 83 patients.
Outcomes	Mean arterial BP. Pregnancy outcomes; GA, birthweight, Apgar score. Incidence of proteinurics and non proteinurics PIH.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Randomization was into three groups: control, low‐dose aspirin, and calcium supplementation in a ratio of 1:2:2 using five unsealed envelopes." Of 500 nulliparous women screened, 369 were randomised; 154 were in calcium group, 132 were in low‐dose aspirin and 83 as control group."
Allocation concealment (selection bias)	Unclear risk	Quote: "Randomization was into three groups; control, low‐dose aspirin, and calcium supplementation in a ratio of 1:2:2 using five unsealed envelopes."
Blinding of participants and personnel (performance bias) All outcomes	High risk	The participants received different interventions. Could not blind both participants and assessors.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Quote: "All randomisation, data collection and data entry were undertaken by the same research assistant with the exception of outcome data, which were entered by the first two authors. The research assistant was therefore blind to the outcome group." It is unclear whether the authors collecting data would have been aware of group assignment.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "Fifty (10%) patients eventually delivered in other hospitals and were therefore not subjected to analysis, as they could not reliably be classified into the 3 outcomes groups. 144, 118, and 75 were in calcium group, low‐dose aspirin, and control groups respectively were included in final analysis." Missing data 18 in 237 = 7.6%.
Selective reporting (reporting bias)	Unclear risk	None identified.
Other bias	Low risk	None identified.