Table 2.

Summarize the possible factors affecting RPL in chromosomal variation.

Types of chromosomal variants		Type	Possible risk factors	Commonly occurring abnormal chromosomes	Reference
Chromosomal abnormalities in embryos	Number anomalies	Aneuploidy (trisomy, monosomy)	Meiotic error, mitotic error and abnormal parental chromosome structure	Chromosomes 13, 16, 18, 21 and 22; x chromosome	[98, 101]
		Polyploid	Double sperm into the egg or meiotic non-separation of the egg; Mitotic non-separation of fertilized eggs		[100]
	Structural anomalies	Abnormal equilibrium translocation structure	Spontaneous mutation by internal and external environmental influences, inherited by couples carrying abnormal chromosome structure		[120]
		Non-equilibrium translocation structural abnormalities
Chromosomal abnormalities in couples	Structural anomalies	Reciprocal balanced translocations	An exchange of DNA segments between nonhomologous chromosomes with no gain or loss of DNA	Chromosomes 11, 6, 4, 1, and 18 were the most commonly translocated chromosomes	[37, 111, 112]
		Robertsonian translocations
		Inversion	Production of unbalanced gametes	Chromosomes 1, 9 and 11 are the most common	[113, 121]
		CNV	Gene deletion or increase	Chromosome 6 duplication was the most common, followed by X chromosome deletion and triplet chromosome abnormalities	[106, 122]
Chromosome polymorphism			Affects mitophase function, sister chromatid binding and chromosome segregation	Inv (9)	[104, 114, 115]
Special chromosomal anomalies		CPM	Placental insufficiency, fetal growth restriction and death		[106]
		XCI	Increased risk of spontaneous abortion in female carriers of X-linked recessive fetal lethal defects	x chromosome	[117, 118, 123], [124]