Eskew 2018.

Study characteristics
Methods	RCT, 2 arms, 100 randomised Setting: Washington University, St. Louis, USA, one centre Recruitment period: September 2013 ‐ July 2017
Participants	Criteria related to previous IVF failure: no Inclusion criteria: women aged 18 or older undergoing a fresh or frozen embryo transfer. Exclusion criteria: third party reproduction, women undergoing a poor responder protocol, or women with a history of an abnormal uterine cavity
Interventions	Study group: endometrial biopsy with an endometrial pipelle in the luteal phase of the cycle prior to embryo transfer Control group: a sham biopsy (placement of pipelle in posterior fornix, withdraw plunger and “scratch” behind cervix 4 times‐ did not insert pipelle into cervix or uterus) during the luteal phase of the cycle prior to embryo transfer If patients were on oral contraceptive pills for their IVF cycle, the procedure was scheduled anytime during the last 7 days or up until 1 day after their pills were discontinued of the cycle prior to embryo transfer. If patients were not on oral contraceptive pills, patients were instructed to check for a luteinising hormone surge and the procedure was scheduled for 7–13 days following in the cycle prior to embryo transfer.
Outcomes	Reported in paper: live birth, clinical pregnancy, miscarriage Obtained by author correspondence: ‐
Notes	Trial registration: authors confirmed the study was not registered Additional concerns and comments: none Funding: NIH funding (5T32HD055172‐09, UL1 TR002345) Author correspondence: yes, with Ashley Eskew (eskewa@wustl.edu) We noticed that the numbers of pregnancies and associated odds ratios were inconsistent in the text of the paper compared to the outcomes table. After contacting the authors we were reassured that the results in the outcomes table were correct; and the authors are contacting the journal to arrange a revision. Publication: full‐text.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote:"randomization was performed using a computer‐generated model with varied block lengths"
Allocation concealment (selection bias)	Low risk	Women were randomised using quote:"consecutively numbered sealed opaque envelopes"
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Sham procedure implemented quote:"Both the patient and the clinician performing the embryo transfer were blinded to the randomization arm"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Only reporting objective outcomes
Incomplete outcome data (attrition bias) All outcomes	Low risk	No attrition: quote:"No patients were lost to follow up"
Selective reporting (reporting bias)	High risk	Authors confirmed trial was not registered, and adverse outcomes such as pain were not reported
Other bias	High risk	Trial stopped early for futility, only after observing challenges with recruitment. Stopping on the basis of O'Brien and Fleming 1979 rule means that the data available for meta‐analysis give a biased effect estimate. Additionally the trial not registered.