If the mother and the father know that they will not be able to mentally handle having and raising the down syndrome child, may the mother abort the fetus? The mother really feels that she would have no life looking at the sick child every day.

There are many various opinions among the poskim on this sensitive issue, for example, R. Moshe Feinstein prohibits it (Igrot Moshe Ch.M. ii, 69), but R. Shaul Yisraeli (Amud HaY'mini, 32), one of the leading poskim who even considered abortion an isur d'oraita (Torah prohibition) of harming and maiming the mother, nevertheless allowed abortion, if the fetus has a great "mum" or "deep retardation", which will bring great pain to the mother or the child, or may endanger the mental health of the mother (R. Sh.Z. Auerbach, R. Goren), even if there is no danger to the mother. R. Avraham Shapira said explicitly that Down's syndrome would fall into this category, and that even if the rabbi agrees with R. Moshe, nevertheless, the parents should be directed to a rabbi who opines in this lenient way (as does the Tzitz Eliezer ix, 51, 3; and xiii, 102, 6; and xiv, 101-102, who cites many sources proving that the entire issue is a rabbinic, not a Torah, prohibition). The parents should be told that often Down's children can lead a relatively normal life, and in fact are really cute, but if they still feel, as you wrote, that the mother would "have no life" and it may be harmful for her mental stability, then they should know that they can surely rely on the many leading poskim who hold that in this case, aborting is allowed. The parents should be notified of this decision as soon as possible (!), for it is easier to justify halachically if done before the end of the 3rd month of pregnancy, but even if it's already later, it's allowed. Also, if possible, it's better to perform the abortion indirectly via "gramma" (e.g. inducing labor, or even injecting chemicals into the uterus) which even some of the stringent authorities would consider a rabbinic prohibition, rather than directly removing the fetus with a scalpel. It's important to stress the seriousness of this halachic decision, and that it may not be used easily as a precedent for other cases, for each case is different, and a competent halachic authority must be consulted for each subjective circumstance. With Love of Israel, Rav Ari Shvat