Demirol 2004.

Methods	RCT Single centre Turkey
Participants	Women who had undergone two or more failed IVF cycles, in which two or more good quality embryos were transferred All the participants had normal HSG (normal intrauterine cavity and bilaterally patent tubes) Age group 24 to 40 years All women had primary infertility
Interventions	Intervention group (N = 210) had office hysteroscopic evaluation of uterine cavity and cervix with intrauterine lesions treated during the office procedure. No additional procedure, such as endometrial biopsy, was mentioned. Hysteroscopy was performed in the early proliferative phase, using saline distension medium All office hysteroscopies were performed 2 to 6 months after the last failed IVF cycle, by the same physician All IVF treatments were carried out on the menstrual cycles after office hysteroscopy Control group (N = 211) did not have hysteroscopy prior to IVF.
Outcomes	Clinical pregnancy rate, first trimester miscarriage rate, normal and abnormal hysteroscopy findings
Notes	Authors were contacted for clarification regarding data, however authors did not respond to emails.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Randomized into two groups using computer generated random numbers".
Allocation concealment (selection bias)	Unclear risk	Not mentioned
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Blinding was not mentioned. However, absence of blinding was unlikely to influence performance bias. Hence, absence of blinding was categorised as low risk for performance bias.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Blinding was not mentioned.However, absence of blinding is unlikely to influence the findings for our primary and secondary outcomes, hence categorized under " low risk" for detection bias.
Incomplete outcome data (attrition bias) All outcomes	Low risk	All randomised participants and losses to follow‐up were mentioned and appeared to be balanced. Intention‐to‐treat analysis was done.
Selective reporting (reporting bias)	Unclear risk	The published protocol for this study was not available. While the prespecified outcomes were reported, the primary outcome (live birth) was not reported.
Other bias	Low risk	We found no other potential sources of within‐study bias. Instituitional ethical board clearance and source of funding was not mentioned.