RT Journal Article SR Electronic T1 Study of the effect of calcium supplementation during pregnancy on the risk of preterm birth or low birthweight infants is inconclusive JF Evidence Based Medicine JO Evid Based Med FD BMJ Publishing Group Ltd SP 186 OP 187 DO 10.1136/ebmed-2012-100778 VO 17 IS 6 A1 Winston Koo YR 2012 UL http://ebm.bmj.com/content/17/6/186.abstract AB