Table 1.

Patient characteristics in the last fresh cycle for the two groups of assisted hatching

	ICM group	TE group
No. of cycles	80	80
IVF cycles/ICSI cycles	56/24	55/25
Mean age of women at vitrification (years) ± SD	29.8 ± 3.2	29.6 ± 4.1
Mean age of women at warming (years) ± SD	30.3 ± 3.3	30.1 ± 4.1
Duration of infertility (yr) (mean ± SD)	4.5 ± 2.9	4.4 ± 3.2
Primary infertility/secondary infertility	43/37	44/36
Tubal factor	51	49
Endometriosis	8	9
Male factor	17	19
Unexplained	4	3
No. of cycles cancelled embryo transfer due to OHSS	42	41
No. of retrieved oocytes (mean ± SD)	20.3 ± 8.1	20.3 ± 8.9
No. of blastocysts vitrified (mean ± SD)	3.7 ± 2.0	3.9 ± 2.7

There were no statistically significant differences between the two groups

OHSS ovarian hyperstimulation syndrome

ICM group: 50 μm opening of the zona pellucida by laser assisted hatching at embryonic pole; TE group: 50 μm opening of the zona pellucida by laser assisted hatching at abembryonic pole