Study	Reason for exclusion
Chen 2004	No reply to written and electronic request; study design, allocation concealment and outcomes unclear
Chen 2009	No reply to electronic request; study design, methods and results not known
Chen 2012	No outcomes of interest
Cui 2007	No reply to electronic request; study design, methods and results not known
Cui 2011	Inadequate randomisation process in study design, based on odd and even numbers
Evans 2005	Lack details on pregnancy outcome, study design, allocation concealment and type of randomisation; no reply to written or electronic letters
Feliciani 2011	No reply to electronic request; study numbers, randomisation process and outcomes unclear
Li 2009	No reply to electronic request; study design, methods and results not known
Omodei 2010	No reply to electronic request; study design, allocation concealment and outcomes unclear
Quintero 2004	Lacks details on allocation concealment and randomisation, no reply to requests for details; crossover design