Schoolcraft 2002

Methods	Parallel randomised controlled trial Prospective participant recruitment Method of sampling of participants was unclear Single‐centre trial performed at the Colorado Center for Reproductive Medicine in Englewood, Colorado, USA Both IVF patients with their own oocytes and oocyte donors were included Unclear whether a power calculation was performed Participants were enrolled in this trial from January 2001 to February 2002. The exact length of follow‐up per participant was not stated, but it was long enough to permit measurement of the trial's proposed outcomes Unclear whether an intention‐to‐treat analysis was performed Unclear whether multiple treatment cycles or only one treatment cycle per participant were included in the trial Trial was supported by Vitrolife
Participants	A total of 175 IVF participants and oocyte donors were recruited for this trial. 141 of them were IVF patients, and 34 were oocyte donors. 91 participants were randomly assigned to the treatment group and 84 to the control group. No loss was reported, so the data on all 175 participants were analysed. Number of transferred embryos was unclear; only the mean number per group was published Age: not reported Not reported whether study concerned primary and/or secondary subfertility Cause and duration of subfertility not reported Trial studied only IVF participants, no participants receiving ICSI. Not reported whether participants had received previous IVF treatment No age analysis was reported
Interventions	Embryo transfer of participants' own or donated fertilised oocytes in G2.3 medium supplemented with EmbryoGlue (0.5 mg/ml HA) versus transfer in G2.3 medium (0.125 mg/ml HA) All embryos were cultured in G1.3 medium Timing of randomisation was unclear Embryos were exposed to the higher concentration of HA just before transfer Transfer was performed on day three of embryo development Donor oocytes were included Unclear whether embryos had to be fresh or if frozen‐thawed embryos were also included All culture and transfer media were manufactured by Vitrolife Mean number of embryos transferred: treatment IVF group 3.9, treatment donor oocytes 3.9; control IVF group 3.3, control donor oocytes 3.2 Pregnancy and implantation rates were determined by demonstration of fetal heartbeat
Outcomes	Secondary outcomes Clinical pregnancy rate: presented as percentage, with number of participants in study group as the denominator Additional outcomes Implantation rate: presented as percentage; denominator was unclear. No raw data available
Notes	Abstract of ASRM conference presentation The primary author was contacted regarding unclear details in published abstract, but further participation was declined. So some uncertainty cannot be resolved
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation into treatment or control group by a computer‐generated randomisation sheet
Allocation concealment (selection bias)	Unclear risk	Allocation was correctly performed, but concealment was unclear
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Blinding was unclear
Incomplete outcome data (attrition bias) All outcomes	High risk	No live births were reported. Length of follow‐up per participant was unclear. No intention‐to‐treat analysis was reported
Selective reporting (reporting bias)	Low risk	Clinical pregnancy and implantation rates were reported in a prespecified way
Other bias	High risk	Trial was commercially funded by Vitrolife. Same transfer media brand was used in treatment and control groups. Transfer media were comparable, with the addition of EmbryoGlue to the treatment group. No multiple pregnancy rate was reported, although multiple embryos were transferred per cycle