Ettinger 2009.

Methods	Type of study: Double‐blind, randomised, placebo‐controlled trial. Method of treatment allocation:not stated Placebo: yes Intention‐to‐treat basis: yes
Participants	Location: Mexican Social Security Institute, Mexico city, Mexico. Time frame: 2001‐2003 670 women were randomised in the first trimester of pregnancy. 334 to the treatment group, and 336 to the placebo group.
Interventions	1200 mg calcium daily (two 600‐mg calcium carbonate tablets) versus placebo.
Outcomes	Maternal blood lead levels at first, second, and third trimester.
Notes	We have not included outcome data from this study as the trial specifically focused on the effects of calcium supplementation on blood lead levels. The study does not address any of the review's primary or secondary outcomes.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not described.
Allocation concealment (selection bias)	Unclear risk	Not described.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Women were randomly assigned to received 1200 mg calcium (2 tabs of 600 mg calcium carbonate tablets) or placebo. Study described as double‐blind.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Placebo‐controlled trial. Study described as double‐blind.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	670 randomised. 565 women completed follow‐up. 557 included in the analysis (83%). Lost to follow‐up in placebo 18%, calcium group 14%.
Selective reporting (reporting bias)	Low risk	None identified.
Other bias	Low risk	None identified.