Lopez‐Jaramillo 1989.

Methods	Type of study: prospective, randomised, double‐blind, controlled clinical trial. Method of treatment allocation: table of random numbers. The containers and the calcium tablets for both groups were prepared in Facultad de Quimica y Farmacia. Stratification: not stated. Placebo: yes, start tablets. Sample size calculation: not stated. Intention‐to‐treat analyses: yes. Losses to follow‐up: 13.2%. Only women with no missing values for any of the covariate and outcome variables were included in the analysis. 49 in calcium group and 43 in placebo group. 6 women in calcium group and 8 in placebo group were eliminated from analysis because they were delivered before 38 weeks.
Participants	Location: antenatal outpatient clinic in the Hospital Gineco‐Obsterica Isdro Aroya in Quito, Ecuador. Time frame: 30 months during 1984‐1986. Eligible criteria: nulliparity, age <  25 years, certain LMP, registration at antenatal clinic for the first prenatal visit before 24 weeks' gestation and residency in Quito (2800 m altitude) for a period of at least 1 year before conception, BP < 120/80 mmHg and free for of any underlying medical disorders based on a comprehensive medical student examination and routine laboratory tests. Exclusion criteria: had history of cardiovascular, renal or endocrinological disease or if they took any type of drug or vitamin/mineral preparation. Total recruited: 106 pregnant women; n = 55 in treatment group, n = 51 in control group.
Interventions	2000 mg of calcium (4 tablets of calcium gluconate daily, 500 mg of elemental calcium) compared with 4 tablets of placebo per day, same size, weight and colour. Started treatment at 23 weeks until delivery.
Outcomes	BP develop PIH. Pregnancy outcomes; weight gain, preterm birth, birthweight, perinatal mortality. Serum ionised calcium concentrations.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Using a table of random numbers each patients was assigned independently in sequence to one of two treatment regimens."
Allocation concealment (selection bias)	Low risk	Quote: "The containers and the calcium tablets for both groups were prepared in Facultad de Quimica y Farmacia."
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Treatment versus placebo. All participants were blinded to intervention.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	The placebo group also received 4 tablets daily of the same size, weight, colour and organoleptic characteristics as calcium tablets.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Quote: "106 women satisfactory met the subject selection criteria. Only women with no missing values for any of the covariate and outcome variables were included in these statistical analysis. 49 in the calcium supplemented group and 43 in the placebo group. Six women in calcium supplement group and eight in the placebo group were eliminated from analysis because they were delivery before 38 weeks." Missing data 14 in 106 = 13.2%.
Selective reporting (reporting bias)	Unclear risk	Comment: not all enrolled participants were analysed.
Other bias	Low risk	None identified.