Gurgan 2019.

Study characteristics
Methods	RCT, 2 arms, 305 randomised Setting: Turkey, private fertility centre, one centre Recruitment period: May 2015 ‐ July 2017 (confirmed by author correspondence)
Participants	Criteria related to previous IVF failure: yes, the failure to achieve a clinical pregnancy after the transfer of at least four good‐quality embryos in a minimum of three fresh or frozen cycles to a woman under the age of 40 years Inclusion criteria: under the age of 40 and follicle‐stimulating hormone (FSH) levels ≤15 IU/mL, and meeting the above RIF condition Exclusion criteria: congenital uterine anomalies, patients with Asherman’s syndrome, patients with uterine cavity distorted by myoma or endometrial polyps, patients with confirmed endometriosis or endometrioma and patients with BMI of <18.5 and >29.9, endometrium thickness of less than 7 mm in the cycle before the cycle
Interventions	Study group: Endometrial injury on the 10‐12th day of late follicular phase in the preceding cycle through office hysteroscopy. Endometrial injury was performed without energy modality (i.e. with scissors). Endometrial injury was performed first on the fundus by cutting into the endometrium (without injuring the myometrium) transversally. Later, three or four vertical incisions were performed 0.5 cm apart each other, on the anterior and posterior walls of the uterus, 1‐1.5 cm away from the fundus and one cut for each lateral wall. Also: standard gynaecological surgical procedures were used to treat recognized pathology Control group: no procedure
Outcomes	Reported in paper: live birth, clinical pregnancy, multiple pregnancy, miscarriage Obtained by author correspondence: ‐ Authors confirmed pain and bleeding were not collected.
Notes	Trial registration: NCT03748238 (registered Nov 2018, registered retrospectively) Additional concerns and comments: one of the trial authors (Makrigiannakis) is the first author of a retracted study, which appears to have been retracted for duplication (Makrigiannakis 2010); the implication of this is unclear. Funding: authors confirmed the study did not receive any specific funding Author correspondence yes, undertaken with muberranamli@hotmail.com Publication: full‐text. A conference abstract was initially identified and the authors provided a report of the trial pending the full publication, and the full‐text paper has now been published.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote:"randomized using a computer‐generated random number sequence (1:1 simple randomization)"
Allocation concealment (selection bias)	Unclear risk	No description. Correspondence undertaken with the authors and it appears that no allocation concealment was in place quote: "Our computer program was very basic. Our numbers were given by turns 0 and 1. So it wasn't hidden and it was possible to see the next allocation if we check computer at that time"
Blinding of participants and personnel (performance bias) All outcomes	High risk	No blinding was employed
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Only objective outcomes reported
Incomplete outcome data (attrition bias) All outcomes	High risk	Three women in the injury group and 9 women in the control group were excluded for refusing their allocation. There was also an imbalance in the number of women with cancelled or failed IVF cycles: 13 in the injury group and 28 in the control group ‐ which could lead to a higher pregnancy rate in the injury group under intention‐to‐treat. Additionally, 13 women in the injury group were excluded post‐randomisation if uterine pathology was detected during the hysteroscopy quote:"Standard gynaecological surgical procedures were used to treat recognised pathology and any patients with surgical intervention other that endometrial injury were excluded from the study."
Selective reporting (reporting bias)	High risk	Registered retrospectively and only listing biochemical pregnancy as an outcome. Live birth reported, however adverse events such as pain not reported. The manuscript states "No hysteroscopy‐related adverse events were reported" but it is unclear whether they measured pain and bleeding.
Other bias	High risk	Trial registered retrospectively