Goto 2009.

Study characteristics
Methods	Study design: RCT Setting: Private IVF clinic Period:NS
Participants	Patient(s): 144 women in their first ART cycle who had at least one blastocyst but who, to prevent the development of ovarian hyperstimulation syndrome (OHSS), had not yet undergone fresh embryo transfer in stimulated cycles. Their blastocysts were therefore cryopreserved for frozen‐thaw embryo transfer in the study cycle. Exclusion criteria: Patients with hydrosalpinx 48 women in the BT group (23 with low‐grade blastocysts, 25 with high‐grade blastocysts) 48 women in the ST group who had culture medium injected into the uterus before BT (19 with low‐grade blastocysts, 29 with high‐grade blastocysts) 48 women in the SEET group (23 with low‐grade blastocysts, 25 with high‐grade blastocysts) Baseline characteristics Age of patient (years) Period of infertility (months) Basal FSH level (mIU/mL) No. of oocytes retrieved No. of oocytes fertilised
Interventions	Injection of embryo culture supernatant and injection of culture medium
Outcomes	Main outcome measure(s): No. of chemical pregnancies Implantation rate per embryo (%) No. of clinical pregnancies Clinical pregnancy rate per transfer (%) Low grade blastocysts High grade blastocysts
Notes	48 women in the BT group who underwent BT (control), 48 women in the stimulation group (ST) who had culture medium injected into the uterus before BT, and 48 women in the SEET group who had ECS injected into the uterus before BT. A single frozen‐thawed blastocyst was transferred in the hormonal replacement cycle in the study. Written informed consent was obtained from the patients, and the entire procedure was examined and approved by the Institutional Review Board (IRB) of Hanabusa Women’s Clinic.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Patients were randomised into three groups using colour‐marble lots drawn by a technician blinded to patient information
Allocation concealment (selection bias)	Unclear risk	Method not described in detail
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not described
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Not described, but unlikely to be biased as the outcome measures are not likely to be influenced by lack of blinding; the outcomes, which are dichotomous, refer to clinical events and their measurement cannot vary between different investigators
Incomplete outcome data (attrition bias) All outcomes	Low risk	Authors report no missing outcome data
Selective reporting (reporting bias)	High risk	No follow‐up until live birth in published data, no miscarriages reported in published data. The study was focused on embryological data. No protocol registered
Other bias	Unclear risk	Consistent with other projects of the same researchers, but insufficient details to make a judgement