Safdarian 2011.

Study characteristics
Methods	RCT, 2 arms, 100 randomised Setting: Iran, hospital, one centre Study period: July 2008 to March 2009 (unclear if recruitment period or whole study period)
Participants	Criteria relating to previous IVF failure: no Inclusion criteria: 20 to 39 year‐old infertile women who were referred to the fertility centre Exclusion criteria: women older than 39 years of age; follicle‐stimulating hormone > 11; endometriosis; hypothalamic amenorrhoea; azoospermic male
Interventions	Study group: pipelle procedure on day 21 menstrual cycle preceding IVF cycle, with use of contraceptive pill before IVF‐embryo transfer treatment Control group: no procedure
Outcomes	Reported in paper: clinical pregnancy Obtained by author correspondence: ‐
Notes	Trial registration: IRCT201008154572N1 (registered Sep 2011, registered retrospectively) Additional concerns and comments: across an apparent 9‐month recruitment period, trial team recruited 11 women per month ‐ which is a reasonably high rate, however not on its own a serious concern. Funding: this project was financially supported by Infertility Center, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran. Author correspondence: Emails sent to corresponding author (shmovahedy@razi.tums.ac.ir) but no reply received Publication: full‐text.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Computerised; participants were randomly selected on the basis of agreement to undergo endometrial biopsy expressed in a written informed consent before the start of the IVF cycle. This wording suggests the allocation was based on the participants agreement or preference, therefore unclear whether truly randomised.
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 reporting objective outcomes
Incomplete outcome data (attrition bias) All outcomes	Low risk	Does not appear to be any attrition
Selective reporting (reporting bias)	High risk	Trial was registered retrospectively and only reported clinical pregnancy, not live birth or any adverse events.
Other bias	High risk	Trial registered retrospectively.