Changes in sex ratio from fertilization to birth in assisted-reproductive-treatment cycles

Table 1 Sex ratio (XY/XX) of genetically diagnosed preimplantation embryos according to the method of fertilization applied and embryo developmental stage

Method of fertilization	Four- to 8-cell embryos^a	Day-5 blastocysts	References
IVF	1.50^b (60/40)		[3]
	Total: 1.50^b (60/40)
ICSI	0.88 (123/140)		[4]
		0.98 (225/229)	[30]
	1.18 (741/629)		[14]
	0.86 (96/112)		[7]
	Total: 1.09 (960/881)	Total: 0.98 (225/229)

^aIn the IVF group, a total of 25 (17 males and 8 females) and 75 (43 males and 32 females) embryos were analyzed at the 4- and 8-cell stage, respectively. In the ICSI group, all the embryos were analyzed at the 8-cell stage.
^bSex ratio of 4- to 8-cell embryos would be 1.29 (66/51) if we consider 17 extra embryos that exhibited abnormal number of X and Y signals in the biopsied cell(s).

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