All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
Abortion is forbidden, so it is not permissible to carry it out unless there is a dire necessity because it is killing a soul which Allaah has forbidden to be killed except by right.
On the other hand, we do not know the basis for the Fatwa that was issued by the person who permitted abortion in the situation which you mentioned in the question. The fact that the fetus will not live after birth more than three days is not a necessity that justifies abortion unless leaving it constitutes a danger for the life of the mother, in which case, aborting it becomes permissible in order to save the mother's life.
In case there is a danger on the life of the mother and the life of other fetuses, we have issued Fatwa 83128 clarifying that abortion is permissible in case of necessity. However, this is not the situation in the case which you mentioned in the question.
Therefore, it is an obligation on the one who caused the abortion, like the mother, and the one who carried it out, like the doctor, to repent to Allaah, the Most High. The one who carried out the abortion is obliged to to pay the blood money which is one-tenth of the blood money of the mother.
However, there is a difference of opinion among the scholars regarding the expiation, but in order to be on the safe side, it is better to pay the expiation.
For more benefit on expiation, please refer to Fatwa 85558.
Finally, it should be noted that the one who is obliged to pay the blood money does not inherit anything from it.
Allaah Knows best.