In my reading, the Church has said that the weight of respected opinion leans towards ensoulment occurring at, or shortly after, conception, but that the whole question is a canard, in that the fetus is engaged in a process of development, so killing it before it has a soul, (if there is a "before") is morally equivalent to killing it after.  So, we have a "probably," and a rather porous claim of equivalency.  If you can steer me towards something in the magisterium that's more robust than that, I'd be grateful.