Table 5.

Primary outcomes of retained studies

Preterm Birth and Low Birth Weight
Outcome 1 No relationship	Outcome 2 Possible relationship	Outcome 3 Positive relationship
Polyzos et al. 2010 da Silva et al. 2017 Chambrone et al. 2011 Iheozor-Ejiofor et al. 2017 (preterm birth) Rangel-Rinc-n et al. 2018 Lopez et al. 2015	Kim et al. 2012 (only in high risk groups) Schwendicke et al. 2015 (only in populations with- high occurrence >20%) Iheozor-Ejiofor et al. 2017 (low birth weight) Shah et al. 2013 BUT (better studies needed to demonstrate cause)	None