Date	Event	Description
29 September 2015	Amended	In response to feedback, we have moved the study Kazemier 2012a, from the ongoing section to studies awaiting classification.
19 March 2015	New citation required but conclusions have not changed	Overall conclusions unchanged, but quality of the evidence in support of an effect of antibiotics for the primary outcomes rated as low to very low.
19 March 2015	New search has been performed	We updated the search and identified four new studies; two references to a single study were excluded because they did not meet the inclusion criteria (Rafalskiy 2013), one was another reference to a previously included study (Elder 1971), and one was a reference to an ongoing study (Kazemier 2012). Methods and 'Risk of bias' table updated. A 'Summary of findings' table was incorporated. The World Health Organization's definition of prematurity of less than 37 weeks has been used.
1 September 2008	Amended	Converted to new review format.
31 January 2007	New search has been performed	We updated the search and identified two new studies. One additional study (Elder 1966) has been included and another excluded (Mohammad 2002). We have moved the LeBlanc 1964 study to the excluded studies because this study did not meet the inclusion criteria.
31 January 2007	New citation required but conclusions have not changed	This review has been extensively rewritten. Low birthweight has been separated from preterm birth as outcomes; subgroup and sensitivity analyses are described and heterogeneity of studies discussed.