New Perspectives of Embryo Sexing Through Morphological Criteria and Sperm Fertilizing Parameters in Mammalian Species: A Review

Predetermining embryo sexing before the time of conception could be controlled before fertilization of the oocyte or detected after fertilization. These methods are expensive, time-consuming and negatively affect the development of embryos. The methods used for embryo sexing are based on sperm separation before fertilizing the oocyte or molecular basis of nuclear or mitochondrial DNA. The selection of spermatozoon fertilizing controls the sex of the zygote in vivo or in vitro matured oocytes. In addition, the detection of embryo sexing is determined through aspiration of one cell from the eight-cell stage embryo and investigated through PCR. The oocyte fertilization by a spermatozoon bearing a Y-chromosome gives male offspring, although that fertilized by a spermatozoon bearing an X-chromosome gives female offspring. The embryonic cell aspiration negatively affected the further developmental competence of embryos. Therefore, establishing a new method for embryo sexing in mammals through measurable morphological criteria (zona pellucida, homogeneity of cytoplasm, previtelline space and stage of development) is a great boon in animals and humans. The success in embryo sexing through morphological criteria maximizes the advantages of assisted reproductive techniques. Therefore, the present review article addresses and discusses the preselection of embryo sexing at the time of conception and their limitation and effects in addition to sperm fertilizing parameters on mammals.