Yeung 2014.

Study characteristics
Methods	RCT, 2 arms, 300 randomised Setting: Hong Kong, academic/research hospital, one centre Recruitment period: March 2011 to August 2013
Participants	Criteria relating to previous IVF failure: no Inclusion criteria: women undergoing IVF for tubal; unexplained or male factor subfertility with normal uterine cavity as shown on saline sonography/hysteroscopy done at baseline Exclusion criteria: presence of hydrosalpinx, endometrial polyp or fibroid distorting uterine cavity; IVF cycles carried out for preimplantation genetic diagnosis; use of donor gametes
Interventions	Study group: endometrial aspiration by pipelle performed on luteinizing hormone +7 in the cycle preceding scheduled IVF treatment Control group: no procedure All women underwent either hysteroscopy or saline sonography within the 3 months before their IVF cycle (information upheld by corresponding author during study presentation at ESHRE 2014)
Outcomes	Reported in paper: live birth, clinical pregnancy, miscarriage (reported as miscarriage per chemical pregnancy), multiple pregnancy, pain, bleeding Obtained by author correspondence: ‐
Notes	Trial registration: HKCTR‐1646 non‐primary registration (registered Jan 2011, registered prospectively); NCT01977976 (registered Nov 2013, registered retrospectively) Additional concerns and comments: the timelines appear to be implausible. Women were recruited until August 2013, followed to live birth, and then the paper was submitted for publication in April 2014. The authors informed us that when they submitted the paper for publication initially, it included only ongoing pregnancy data. During the revision phase the authors updated the manuscript with the live birth data, the latest of which was born in May 2014 and the paper was accepted in July 2014 ‐ therefore the timelines are not implausible. Funding: Small Project Funding 201309176012 of the Committee on Research and Conference Grants, University of Hong Kong. Author correspondence: limited correspondence undertaken with Dr Yeung in previous update Publication: full‐text.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Paper states quote: "Computer‐generated randomization list with blocks of 10" was used
Allocation concealment (selection bias)	Low risk	Paper states quote: "sealed envelopes" were opened "by a research nurse not involved in the clinical management of the subjects." Unclear if SNOSE ‐ however envelopes were opened by a third party
Blinding of participants and personnel (performance bias) All outcomes	High risk	No blinding was employed
Blinding of outcome assessment (detection bias) All outcomes	High risk	The outcome of pain during the procedure and bleeding were self‐reported by participants who were not blind to their treatment allocation
Incomplete outcome data (attrition bias) All outcomes	Low risk	There was imbalance in the number of participants withdrawing from the study (19 in the intervention arm and 6 in the control arm), however this is minimal and did not affect the results
Selective reporting (reporting bias)	Low risk	Trial was registered retrospectively, however all review outcomes reported
Other bias	Low risk	Trial registered prospectively with a non‐primary trial register (HKCTR). The authors only realised this registration was not adequate when preparing for manuscript submission at which time they registered the trial retrospectively (NCT). The authors provided the ethics approval letter and therefore we have graded this as low‐risk.