L‐Jaramillo 1997.

Methods	Prospective, randomised, double‐blind, placebo‐controlled trial.
Participants	Hospital setting in Quito Ecuador, women recruited 1990‐1995. Inclusion criteria: age < 17.5 years; nulliparous; first prenatal visit before 20 weeks' gestation; certain menstrual dates; residency in Quito for at least 1 year; BP =/< 120/80 mmHg; no underlying medical disorders; no drug, mineral or vitamin therapy. Average daily calcium intake in this population is 51% of the recommended dietary allowance.
Interventions	Elemental calcium 2 g daily as calcium carbonate from 20 weeks (n = 134), vs placebo tablets (n = 140).
Outcomes	Pre‐eclampsia (BP > 140/90 mmHg on 2 occasions > 6 hours apart, and proteinuria > 300 mg/L (> 1+ on dipstick on 2 occasions 4‐24 hours apart)). BP recorded as mean of 2 measurements, 2 minutes apart, in the right arm, in the sitting position (1st and 5th Korotkoff sounds). Maternal serum ionised calcium at 38 weeks was calcium group mean 1.23, SD 0.02 mM vs placebo 1.16, 0.02; umbilical cord serum ionised calcium levels were calcium 1.44, 0.04 vs placebo 1,37, 0.03; gestational length was calcium 39.6, 0.4 vs placebo 38.7, 0.3.
Notes	Quito, Ecuador (altitude 2800 m). 1990 to 1995. Source of funding: supported by the Safe Motherhood Program, World Health Organization. CoI: not stated.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Random number table used to assign each participant independently in sequence to calcium or placebo regimen
Allocation concealment (selection bias)	Low risk	Adequate. Tablets similar in weight, colour, size. Containers and tablets prepared by the Department of Chemistry and Pharmacy, Central University of Ecuador
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Double‐blind
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Double‐blind
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	274 recruited, 260 analysed
Selective reporting (reporting bias)	Unclear risk	Only participants with no missing values were included in the analyses (125 in calcium group and 135 in placebo group).
Other bias	Unclear risk	14 withdrawals after randomisation: 12 by change to another hospital or private medical doctor, 2 by non‐compliance. 9/134 (6.7%) were from the calcium group and 5/140 (3.6%) from the placebo group.