Thus far we have discussed cases in which a fetus clearly suffers from a specific condition. However, sometimes all that we can know is that a fetus is at risk of being ill. For example, if the mother contracted German measles in the first month of her pregnancy, there is a fifty percent chance that the child will be born with birth defects. Additionally, sometimes an ultrasound raises a concern that a fetus might have very serious problems, but also may be perfectly healthy.
According to those who take the restrictive view, when we know for sure that the fetus is very sick – and certainly when we are not sure – abortion is still prohibited.
According to those who espouse the permissive approach, since abortion is prohibited as a form of ḥavala or hashḥata, not murder, it is permitted when there is a great need. Therefore, even in an uncertain case, if there is reasonable concern that the fetus has a serious condition that would condemn it to a life full of suffering, abortion is permitted (Amud Ha-yemini §32).
This is relevant when there is no possibility of reaching a clear conclusion regarding the condition of the fetus. But usually, if the parents wait until week twenty and reevaluate the fetus’s condition, the doctors will know much more. Therefore, abortion is forbidden before that point. For example, if the mother contracts CMV (Cytomegalovirus) in her first trimester, the odds are about forty percent that the fetus will contract the virus as well. If the fetus does contract the virus, the odds are about ten percent that it will suffer abnormalities serious enough to warrant abortion according to the permissive approach. Therefore, one must wait until the twentieth week of pregnancy. If it becomes clear that the fetus suffers from serious abnormalities, termination of the pregnancy would be permissible according to the permissive approach (as explained in section 4 and n. 7). As we saw in section 3, in pressing circumstances one may rely on the permissive view, as it is better grounded in the Talmud and halakhic literature.