Ashrafi 2017.

Study characteristics
Methods	Randomised controlled trial, 2 groups, set in Royan Institute and Imam‐Khomeini Hospital affiliated with Tehran University of Medical Sciences, Iran January 2013 to January 2014 Number of participants randomised: 167 Number of participants analysed: 150
Participants	Inclusion criteria: ≥ 2 intrauterine insemination (IUI) failures (no chemical or clinical pregnancy); normal uterine anatomy and hysterosalpingography Exclusion criteria: > 40 years old; diagnosis of uterine lesions such as submucosal leiomyoma; previous diagnosis of moderate to severe pelvic endometriosis; body mass index ≥ 35 kg/m²; severe male factor infertility; smoking habit; alcoholism Cause of infertility: polycystic ovary syndrome (PCOS), unexplained, mild male factor, mixed (male and female factors)
Interventions	Intervention group: endometrial scratch performed on Day 8 or 9 of the IUI cycle Control group: no endometrial scratch Both groups: controlled ovarian hyperstimulation (COH) from Day 3 to 7 with clomiphene citrate (Ovumid) 50 mg twice a day or letrozole (Letrofem) 2.5 mg/d; from Day 6 to 8, 1 to 2 ampoules human menopausal gonadotropin (Menopur) per day given according to ovarian response. When follicles are 18 mm, 10.000 units human chorionic gonadotropin (hCG, Choriomon) was given. IUI was performed 36 hours after hCG. Luteal phase support was performed using Cyclogest 400 mg daily Degree of endometrial injury: pipelle Timing of endometrial injury: follicular phase (Day 8 or 9 of the stimulation/IUI cycle) Study length: 1 cycle Type of conception: IUI
Outcomes	Reported in the paper: Clinical pregnancy (gestational sac with heartbeat on ultrasound) Miscarriage (early loss of pregnancy before 12 weeks' gestation)
Notes	Funding source: not reported Conflict of interest: study authors declare no conflict of interest Trial registration: IRCT201507271141N19 (retrospectively registered) Author correspondence was undertaken, but we did not receive a response
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "patients were randomly allocated into two groups using block randomisation with a block of size 4, and numbered opaque sealed envelopes. The list of codes inside the envelopes was generated by computer"
Allocation concealment (selection bias)	Low risk	Numbered opaque sealed envelopes were used, ensuring adequate concealment of allocation
Blinding of participants (performance bias)	High risk	Quote: "the study was not performed blind" We anticipate that lack of participant blinding introduced performance bias
Blinding of personnel (performance bias)	High risk	Quote: "the study was not performed blind"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "efforts were made to ensure that the assessor researcher was unaware of the studied groups" Albeit outcomes were unlikely to be influenced by lack of blinding, as there were no patient‐reported outcomes
Incomplete outcome data (attrition bias) All outcomes	Low risk	Missing outcome data were balanced in numbers, with similar reasons for missing data across intervention groups; therefore the study was rated as having low risk of attrition bias
Selective reporting (reporting bias)	Unclear risk	The trial was registered retrospectively
Other bias	Low risk	We did not identify any other potential sources of bias