the optional decrease of the number of embryos; study of the principles of its illegitimacy in islamic jurisprudence

although using of treatment methods of infertility makes the realization of the hope of having children more possible, it makes the infertile families face the multiparity problem. the medical society is trying to decrease the numbers of embryos to fertilize the infertile couples for decreasing their anxiety about having some babies. in this study, we are trying to study the reasons of legality or illegality of decreasing of the numbers of embryos. according to the juristic considerations:1)the first principle which must be observed in the affairs which deal with human life is precaution rather than acquittance. so, we must be aware in confrontation with the issue of discredit to the legality of decreasing of the numbers of embryos. the reason is that the theme is killing of an existent that can be changed into a perfect human being. in fact, each action which leads to his/her demolition must be avoided. 2) the most important reason for verifying of illegality of decreasing of the numbers of the embryos is considering the embryo as a person. although the existent inside the womb cannot be considered as a perfect human being, he/she is a potential human being which will have moral personalities, and subsequently juristic-legal personality, in the passing of his/ her embryonic period. 3) the parents` consent is not enough for confirmation of the license of deceasing of the numbers of embryos. the reason is that their genetic dominion on their sexual liquids doesn’t give them freedom to his/her demolition after spermatogenesis.