The selection of sex is the practice by means of which there is chosen the sex (masculine or feminine) of a child before the conception. The selection of sex can be adapted in pairs(couples) who want to avoid to transmit genetic problems that are related to a particular sex (medical selection of sex), as well as those that want to have a son of the sex opposite to that of an existing son (elective selection of sex). Later, he(she) will find information about the prenatal selection of sex, included an explanation of the principal available methods of selection of sex nowadays. Selection of sex (MICROSORT) Regarding the selection of sex, two basic reasons exist behind the decision to choose a son of a specific sex. When a pair(couple) tries to conceive and wants to use the selection of sex to avoid certain genetic or chromosomal problems in his(her,your) baby, the process is named a medical selection of sex. Tay-Sachs's childhood disease is an example of a genetic fatal disorder that can be transmitted without knowing it across the parents, but that can be avoided by means of the prenatal selection of sex.