This is true, but for decision-making purposes I'd like to know the numbers, i.e., the ratio of prevented ovulations to prevented implantations. If, for example, the overall rate of prevented implantation (in # of occurrences per unit time) is lower than the rate of spontaneous miscarriages would be when using no contraception, then the pill is saving lives.
The minipill, Norplant and other progestin only products are likely 100% abortifacient. Other hormonal contraceptives are likely abortifacient between 10 to 50% of cycles.
Regardless the deaths by blood clots, strokes, heart attacks, and the huge increase in breast and cervical cancer outweigh any possible benefits from hormonal contraceptives by orders of magnitude.