Table 2: Quality assessment of the included studies.

Study/Year
Reference		 Random sequence generation Allocation concealment Blinding of participants and personnel Blinding of outcome assessment Incomplete outcome data Selective reporting Other bias
Vermund 1991 [19]
Miott 1996 [21]
Chiasson 1997 [47]
Uberti-Foppa 1998 [23]
Cu-Uvin 1999 [2]
Warren 2001 [39]
Conley 2002 [22]
Branca 2003 [26]
Viscidi 2003 [27]
Viscidi 2003b [28]
Ohmit 2003 [44]
Harris 2005 [29]
Watts 2005 [24]
Watts 2006 [25]
Didelot-Rousseau 2006 [31]
Ng´andwe 2007 [32]
Sha 2007 [16]
Singh 2009 [33]
Desruisseau 2010 [35]
Djigma 2011 [34]
Nowark 2011 [45]
Gallo 2011 [40]
Oliveira 2011 [17]
Chiduo 2012 [30]
Blitz 2013 [36]
Hu 2013 [18]
Apalata 2014 [20]
Benning 2014 [41]
Mackelprang 2015 [43]
Masson 2015 [42]
Alczuk 2015 [15]
Massad 2016 [37]
Reimers 2016 [38]
Kriek 2016 [46]
Alcaide 2016 [14]

:High risk of bias: Unclear risk of bias: Low risk of bias