Wan 2014.

Study characteristics
Methods	Prospective randomised Not known whether participant had first or previous treatment IVF or ICSI June 2010 to August 2011 Fresh ET done with cleavage stage ‐ no result provided Blastocysts vitrified and randomised in 2 groups, then FET after warming
Participants	203 infertile couples
Interventions	Control group ‐ no LAH (n = 102) Experimental group ‐ had LAH (n = 101) (2 blastocysts did not survive after warming, 3 were lost to follow‐up), so total results n = 96 2 embryos (blastocysts) transferred in both groups after warming
Outcomes	Live birth rate, multiple pregnancy rate, clinical pregnancy rate, miscarriage rate
Notes	Study author contacted but no response received Figure 2 and tables are contradictory due to number of participants in each group as stated in the paper; we accepted the data as described in the text and presumed that there was an error in Figure 2
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "during the study period, 203 patients who met the inclusion criteria were enrolled and randomly divided into two groups"
Allocation concealment (selection bias)	Unclear risk	Paper states patients "were randomly divided into two groups" but no further information provided
Blinding (performance bias and detection bias) All outcomes	Unclear risk	No information provided
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	5 patients in the QLAH group who met the exclusion criteria were excluded from analyses (2 patients had no surviving blastocysts for transfer after warming) but 3 patients were lost to follow‐up. No patients in the control group were lost to follow‐up
Selective reporting (reporting bias)	Low risk	No response from study author on further details. Live birth rate reported
Other bias	Unclear risk	Description of population ‐ unclear whether they had first or previous treatment

AH: assisted hatching.
ART: assisted reproductive technology.
ASRM: American Society for Reproductive Medicine.
CM: cosmetic micromanipulation
ET: embryo transfer.
FET: fresh embryo transfer.
FSH: follicle‐stimulating hormone.
GS: gestation sac
hCG: human chorionic gonadotropin.
ICSI: intracytoplasmic sperm injection.
ITT: intention‐to‐treat.
IVF: in vitro fertilisation.
LAH: laser‐assisted hatching.
QLAH: quarter laser‐assisted hatching.
TV: transvaginal.
TVS: transvaginal sonography.
USS: ultrasound scan.
ZP: zona pellucida.
Mean age given in years (standard deviation).
Note: only arms where all or no embryos transferred and were treated with AH were accepted for data extraction.