FIRST, abortion is never safe for preborn humans — it dismembers, suctions, or poisons them to death.
SECOND, even if an argument could be made that legal abortion is safer for the woman, if abortion ends an innocent human being’s life, then it isn’t ethical to legalize killing in order to make it supposedly safer for those participating in it.
THIRD, abortion, whether legal or illegal, carries the risk of negative effects to women’s health. In other words, some women were hurt or killed in illegal abortions and some women are hurt and killed by legal abortions, too. 
FOURTH, the number of women who died from illegal abortions prior to Roe v. Wade (1973) was greatly inflated by those lobbying for the legalization of abortion.