Table 1.

Characteristics of the included studies

Study	Design	Outcome	ET stage	Vitrification	Quality scores
Cobo et al. [13]	R	CPR, IR, MR, LBR, OPR	day2/3+day5/6	Cryotop	7
Lee et al. [27]	R	CPR	day3+day5	No statement	6
Vos et al. [24]	R	LBR	day3+day5	No statement	8
Sugiyama et al. [29]	R	CPR, IR, MR, LBR	day3+BL	Cryotop	6
Shaw et al. [28]	Prospective study	CPR, IR, MPR, MR	day3+day5	No statement	7
Tong et al. [30]	R	CPR, IR, MPR	CL+BL	Cryotop	7
Desai et al. [25]	R	CPR, IR	day3+day 5/6	Cryoloop	6
Desai et al. [26]	R	CPR, IR, MPR, MR, LBR, OPR	CL+BL	Rapid-i+cryoloop	7

CL cleavage stage ET, BL blastocyst stage ET. R retrospective study