Motives of abortion are many and various. In order to be taken into consideration by the Sharia, those motives must be proved, their results must be certain and the over all benefits of abortion must be greater than neglecting these motives. Even when the above factors are available, the period of pregnancy should be considered: whether abortion will take place before the time of breathing spirit in the fetus or after that. Spirit is believed to be breathed when the fetus has completed 120 days in the womb.
Concerning abortion before spirit breathing, the more accepted opinion is that it is prohibited, because the zygote is growing up to reach the stage of having the spirit breathed in it. If modern medical techniques have definitely assured that the fetus sustains dangerous genetic defects that would render the fetus incompatible with normal life and that these defects would be genetically transferred to its family, abortion then, is permitted before spirit is breathed, rather it will be obligatory.
After the spirit is breathed, abortion is absolutely prohibited through any means that causes its delivery from the womb, unless there is a decision by professional medical consensus states that the fetus is extremely harmful to the mother and threatens her life, abortion, then, is not only an option, but a must. This of course excludes abortion of illegitimate pregnancy.