2015 Aug 17

New citation required and conclusions have changed

This review is an update of the previous Cochrane systematic review (Walker 2009) that included 18 RCTs.

One previous author (Kristine Aas‐Eng) decided not to update the review. Two new authors: Sharon R Lewis and Anastasia Price have joined the review team

We altered the review eligibility criteria.

We included 32 studies that met our new eligibility criteria; 19 of these from our 2014 search 13 from Walker 2009. There are four studies awaiting classification and four ongoing studies. We excluded a total of 33 key studies; five from Walker 2009 due to the change in criteria and 27 from the 2014 search.

We reran the search in 2015 and found a further seven studies which are awaiting classification. There are now 11 studies awaiting classification.

We updated the methods to take into account Revman 5.3 and carried out 'Risk of bias' assessment to include the 13 studies from Walker 2009. We extracted data from eligible studies and completed meta‐analysis, leading to a different conclusion.

2015 Aug 17

New search has been performed

The original search was to July 2008 (Walker 2009). In this updated review we reran the searches until August 2014.

2011 Feb 15

Amended

Contact details updated.

2008 Oct 29

Amended

Converted to new review format.