Date	Event	Description
31 October 2014	New search has been performed	Search updated. Seven new reports identified from the updated search: two reports of one new trial included (Egypt 2014); one new trial excluded (Naher 2012) and four new reports of existing trials added. Methods have been updated. A 'Summary of findings' table incorporated.
31 October 2014	New citation required but conclusions have not changed	The inclusion of one new trial (Egypt 2014) did not change the conclusions.
9 November 2011	New search has been performed	Search updated. Three new trials included (China 2001; Ghana 2009; Iran 2010) and four new trials excluded (Mahmoudian 2005; Van Vliet 2001; Villamor 2006; Yalda 2010).
9 November 2011	New citation required but conclusions have not changed	New authors helped to update this review.
1 July 2011	Amended	Search updated. Thirteen trial reports added to Studies awaiting classification.
6 November 2008	Amended	Converted to new review format.
20 December 2006	New search has been performed	Search updated. Nine new studies have been added to the original seven included studies, plus one previously excluded study (USA 1985) has now been included, making a total of 17 studies included in the 2006 update. A total of 11 studies have been excluded in this update and two studies have been placed in Studies awaiting classification. The Background and Methods sections have been expanded in this update, and additional outcomes have been added. The title has been changed from 'Zinc supplementation in pregnancy' to 'Zinc supplementation for improving pregnancy and infant outcome'. The conclusions regarding the effect of zinc supplementation on reducing preterm birth have been slightly strengthened.