Answer:
   
   [Based on material in [5]Contemporary American Reform Responsa by
   Rabbi Walter Jacob, publ. by CCAR]:
   
   The Reform Movement has had a long history of liberalism on many
   social and family matters. Reform feels that the pattern of tradition,
   until the most recent generation, has demonstrated a liberal approach
   to abortion and has definitely permitted it in case of any danger to
   the life of the mother. That danger may be physical or psychological.
   When this occurs at any time during the pregnancy, Reform Judaism
   would not hesitate to permit an abortion. This would also include
   cases of incest and rape if the mother wishes to have an abortion.
   
   Twentieth century medicine has brought a greater understanding of the
   fetus, and it is now possible to discover major problems in the fetus
   quite early in the pregnancy. Some genetic defects can be discovered
   shortly after conception and more research will make such techniques
   widely available. It is, of course, equally true that modern medicine
   has presented ways of keeping babies with very serious problems alive,
   frequently in a vegetative state, which brings great misery to the
   family involved. Such problems, as those caused by Tay Sachs and other
   degenerative or permanent conditions which seriously endanger the life
   of the child and potentially the mental health of the mother, are
   indications for permitting an abortion.
   
   Reform Judaism agrees with the traditional authorities that abortions
   should be approached cautiously throughout the life of the fetus. Most
   authorities would be least hesitant during the first forty days of the
   fetus' life (Yeb. 69b; Nid. 30b; M. Ker. 1.1; Shulhan Arukah Hoshen
   Mishpat 210.2; Solomon Skola, Bet Shelomo, Hoshen Mishpat 132; Joseph
   Trani, Responsa Maharit 1.99, Noam 9 pp 213ff, etc.). Even the strict
   Rabbi Unterman permits non-Jews to perform abortions within the forty
   day periods (Rabbi Unterman, op. cit., pp 8ff).
   
   From forty days until twenty-seven weeks, the fetus possesses some
   status, but its future remains doubtful (goses biydei adam; San. 78a;
   Nid 44b and commentaries) as we are not sure of this viability. Reform
   Judaism must, therefore, be more certain of the grounds for abortion,
   but would still permit it.
   
   It is clear from all of this that the traditional authorities would be
   most lenient with abortions within the first forty days. After that
   time, there is a difference of opinion. Those who are within the
   broadest range of permissibility permit abortion at any time before
   birth, if there is serious danger to the health of the mother or
   child. Reform Judaism is in agreement with that liberal stance. Reform
   Judaism does not encourage abortion, nor favor it for trivial reasons,
   or sanction it "on demand".