Cattoli 1994.

Methods	Single‐centre parallel RCT
Participants	100 women Inclusion criteria: women who had cryopreservation of embryos following IVF treatment Exclusion criteria: not stated Mean number of transferred embryos per woman: similar, HT group 2.7 ± 0.0 (1‐4 embryos), natural cycle group 2.8 ± 0.8 (1‐5 embryos)
Interventions	FET HT cycle (56 women (64 cycles)) Natural cycle FET (44 women (50 cycles))
Outcomes	Clinical pregnancy rate per woman Multiple pregnancy rate per pregnancy
Notes	This was an abstract. The review authors contacted the first author requesting more data but as this study was not published and was presented in 1994, the study author could not supply any more data.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Process involved in random sequence generation not reported
Allocation concealment (selection bias)	Unclear risk	Methods used in allocation concealment not reported
Blinding (performance bias and detection bias) All outcomes	Unclear risk	No information provided on the blinding of participants and personnel
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	No reports on number of missing outcome data and reasons for drop out or exclusion from study
Selective reporting (reporting bias)	Unclear risk	Insufficient information reported to arrive at a judgement
Other bias	Unclear risk	Insufficient information reported to arrive at a judgement