Xu 2015.

Study characteristics
Methods	RCT, 2 arms, 30 randomised (additional non‐randomised control arm not used) Setting: China, hospital/academic setting, one centre Recruitment period: July 2012 and July 2013
Participants	Criteria related to previous IVF failure: no Inclusion criteria: age younger than 40 years,FSH less than 10 IU/L, failure of endometrial thickness to reach 7 mm by regular methods (in a prior cycle); no signs of submucosal uterine myoma, uterine malformations, endometrial polyps, or obvious intrauterine adhesion by transvaginal ultrasound or diagnostic hysteroscopy, and no signs of other diseases, which could have affected endometrial growth; and no contraindications for granulocyte colony‐stimulating factor treatment (e.g. chronic neutropenia, sickle cell disease, renal disease and history of malignancy). Exclusion criteria: ‐
Interventions	Study group: pipelle procedure and granulocyte colony‐stimulating factor instillation prior to ovulation (when dominant follicle of 12 mm seen)Control group: granulocyte colony‐stimulating factor instillation prior to ovulation (when dominant follicle of 12 mm seen)
Outcomes	Reported in paper: live birth, clinical pregnancy, miscarriage Obtained by author correspondence: ‐
Notes	Trial registration: does not appear to be registered Additional concerns and comments: two of the authors have had two separate papers retracted previously. One was for duplication with another paper they authored in a different journal (PLOS One 2020), and the second was for plagiarisation of a paper that was written by a different author group in a different journal (Zhao 2015). Funding: None stated Author correspondence: Attempted but unsuccessful (lisayanping@sina.com) Publication: full‐text.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Described as randomisation with quote: "a randomized number table"
Allocation concealment (selection bias)	Unclear risk	No description
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Although the description of the procedures suggest the procedure may have blinded participants to their allocation, it is not specifically stated that they were blinded and it is unclear whether participants were informed of their trial allocation
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Only objective outcomes reported
Incomplete outcome data (attrition bias) All outcomes	Low risk	Three participants had cancelled cycles; there was no other attrition
Selective reporting (reporting bias)	High risk	Trial does not appear to be registered, and important outcomes such as multiple pregnancy and adverse events not reported
Other bias	High risk	Trial not registered. Additionally, there are concerns about the retractions made of papers written by these authors on two previous occasions.