First, maternal mortality from all causes, including abortion fell dramatically long before abortion was legalised as a result of better medical care.Pregnancy and birth is not without danger. Modern medical practices have reduced the harms to both mother and baby.
Second, many so called ‘back-street abortions were actually carried out ‘illegally’ by ‘skilled professional’ nurses and doctors using surgical instruments in sterile conditions.
Third, legalising abortion did not eliminate all maternal deaths, as some women now began to die of legal abortions, and in addition there was still a trickle of illegal abortions.
If abortion is the intentional killing of a human person, the murder of a fetus, then the unintentional death of the persons involved in the activity is not an argument for legalising abortion. However it seems that maternal deaths following abortion are not even related to the legality of abortion. Therefore are no grounds to propose legalising abortion anticipating that maternal mortality might decrease.