Elnahas 2017.

Study characteristics
Methods	Randomised into 2 groups on day of ET using sealed envelope but no further details No information on random sequence generation No information about centres Unclear whether participants were blinded Unclear whether outcome assessor blinded No power calculation documented Published full paper
Participants	160 patients undergoing frozen ET after IVF using Day 3 embryos. Age 18 to 40 years, following first IVF pregnancy, following 1 implantation failure, or following postponement of transfer to avoid sequelae of OHSS Only included excellent (≥ 8 cells and fragmentation < 10%) or good (≥ 8 cells and fragmentation between 10% and 20%) quality Day 3 embryos Mean age: control group 31.7, AH group 31.0
Interventions	LAH 1 hour before embryo transfer, thinning of zona pellucida at only one‐eighth of its surface (no breaching) Control – 80 women LAH – 80 women
Outcomes	Clinical pregnancy (defined by transvaginal ultrasound scan on fourth and sixth weeks to detect IU GS and fetal pulsations)
Notes	Mean age: LAH group 31.02, non‐LAH group 31.71
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No information given
Allocation concealment (selection bias)	Low risk	Sealed envelopes used
Blinding (performance bias and detection bias) All outcomes	Unclear risk	No information about clinician or participant blinding nor blinding of outcome assessors
Incomplete outcome data (attrition bias) All outcomes	Low risk	Outcomes reported for all patients
Selective reporting (reporting bias)	High risk	No multiple pregnancy, miscarriage, or live birth data given. Implantation rates given as percentages only