Lopez‐Jaramillo 1997.

Methods	Type of study: a prospective, randomised, double‐blind, controlled clinical trial. Sequence according to random numbers table. Method of treatment allocation: used a table of random numbers to assign each patient independently in sequence to 1 of 2 treatment regimens. Treatment assignment was double‐blind, with composition of tablets unknown to the patients and to all clinical personnel involved in the study. The containers and tablets were prepared in the Facultad de Quimica y Farmacia, Universidad Central del Ecuador. Stratification: not stated. Placebo: yes, starch tablets. Sample size calculation: not stated. Intention‐to‐treat analyses: no. Losses to follow‐up: yes, 14 in 274 = 5.1%.
Participants	Location: Hospital Gineco‐Obstetrico Isidro Ayora in Quito, Ecuador. Time frame: 56‐month period between 1990 to 1995. Eligible criteria: age < 17.5 years, nulliparity, normal single viable pregnancy with known menstrual period date (LMP), registering at antenatal clinic before 20 weeks of gestation, residency in Quito (2800 m altitude) for a period of at least 1 year before conception, BP < 120/80 mmHg and free from any underlying medical disorders, based on a comprehensive medical examination and laboratory test. Exclusion criteria: had history of cardiovascular, renal or endocrinological disease or if they took any type of drugs or vitamin/mineral preparations. Total recruited: 274 pregnant teenagers were randomised; 14 women failed to complete the protocol (3 changed residence, 7 changed to a private hospital, 2 changed to hospital of social insurance, 2 by non‐compliance to treatment); only 260 completed the study, 125 girls received 2000 mg calcium, 135 girls in control group.
Interventions	2 g calcium (4 tablets of calcium carbonate per day, 500 mg of elemental calcium) compared with 4 tablets of placebo (contained lactose and granulated starch) per day, same size, weight, colour and organoleptic characteristics as calcium tablets.
Outcomes	Incidence of PIH. Serum ionised calcium concentrations. Pregnancy outcomes; GA, weight gain, birthweight, fetal mortality. Side effects of calcium.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "We used a table of random numbers to assigned each patient independently in sequence to one of two treatment regimens."
Allocation concealment (selection bias)	Low risk	Quote: "The containers and tablets were prepared in the Facultad de Quimica y Farmacia,Universidad Central del Ecuador."
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "We used a table of random numbers to assigned each patient independently in sequence to one of two treatment regimens." Quote: "Treatment assignment was double‐blind, with the composition of the tablets unknown to the patients and to all clinical personnel involve in the study."
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "Treatment assignment was double‐blind, with the composition of the tablets unknown to the patients and to all clinical personnel involve in the study."
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "274 teenagers were  randomised and then 14 women failed  to completed the protocol (3 changed the residence, 7 changed to the private hospital, 2 changed to hospital of  social insurance, 2 by non‐compliance to treatment) then only 260 completed the study; 125 girls received 2000 mg calcium, 135 girls in the control group." Missing data 5.1%. The authors did not provide information about how many people were missing in each group.
Selective reporting (reporting bias)	Low risk	None identified.
Other bias	Low risk	None identified.