Karim Zadeh 2008.

Study characteristics
Methods	RCT, 2 arms, 160 randomised Setting: Iran in an academic setting Recruitment period: not described
Participants	Criteria related to previous IVF failure: yes, at least 2 prior implantation failures Inclusion criteria: at least 2 prior implantation failures Exclusion criteria: ‐
Interventions	Study group: Novak endometrial suction curettage during the secretory phase in a non‐medicated cycle before IVF/ICSI Control group: no intervention
Outcomes	Reported in paper: Clinical pregnancy Obtained by author correspondence: ‐
Notes	Trial registration: does not appear to be registered Additional concerns and comments: one of the authors is an author on a paper which has been retracted for duplication, as it was very similar to another paper by the same author group in a different journal (Mohsenzadeh 2018). Funding: no description Author correspondence: ‐ Publication: abstract only
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Method of randomisation was not described
Allocation concealment (selection bias)	Unclear risk	No description
Blinding of participants and personnel (performance bias) All outcomes	High risk	No blinding employed
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Only objective outcomes reported
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	It is unclear whether there was an attrition or dropout
Selective reporting (reporting bias)	High risk	Trial not registered and important outcomes such as live birth and adverse events not reported
Other bias	High risk	Published only as a conference abstract with limited detail; no further information could be retrieved from study authors. Trial not registered. Authors are also co‐authors of a retracted paper.