When contraceptive pills were introduced, they were sold as 'birth control' pills, and IUD's were sold as birth control/contraceptive devices ... and they (the pills) did have some preventative effect, holding off ovulation (staving off the release of an egg, to prevent fertilization). But the secondary effect (not to be confused with a lesser number of prevented pregnancies then miscarriages/abortions) was to create a uterine lining inadequacy via hormonal intervention, which usually resulted in termination of any implantation by preventing the uterine circulatory buildup that follows implantation.
In short, contraceptive pills have always been an early form of abortifacient method since the greater percentage of effect is to starve the conceptus of life support from the woman's body. The IUD's worked to create an irritation of the lining, so that an implanted new individual human life would not be able to generate sufficiet nourishment from an iritated lining. These new chemical introductions are primarily effective doing the same thing, and it's instructive to see that they are still being pushed as 'contraception' when they are actually abortifacients.
sufficiet nourishment from an iritated = sufficient nourishment from an irritated