Ethical issues in abortion involve a constant battle between freedom and life.
Pro-choice people are for freedom. They consider it unethical to take away a woman's right to decide over their own body.
"The basis for all freedom is the governance over one's own body and everything that is in it. The opposite is the condition of a slave." - Katti Anker Møller, Norwegian pro-choice activist.
While pro-life people are for life. They consider it unethical to kill a growing life. Stating that it is the very same as murder. Despite many of them ignoring the very fact that without legal, safe abortion, many women will end up killing themselves through unsafe, usually self-performed abortions, or in attempts to cause miscarriage.
These will always be the main ethical issues of abortion, sadly.