Jelinkova 2002.

Study characteristics
Methods	Single‐centre randomised trial
Participants	255 IVF participants only; at least 2 previous failures Age: AH 32.3 (4.24), control 32.1 (3.16) Germany
Interventions	AH (chemical removal by acid; complete zona breach) AH: 128 women Control: 127 women
Outcomes	Clinical pregnancy rate, implantation rate
Notes	Attempted to contact author about this study No. of embryos transferred: AH 2.2; control 2.2
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation stated
Allocation concealment (selection bias)	Unclear risk	Unclear; no details
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Unclear whether participants were blinded
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Not stated
Selective reporting (reporting bias)	Unclear risk	Original protocol not viewed. Live birth not reported, so not sure if it was planned
Other bias	Low risk	None identified