While a lot of people apparently don't know the facts, the most commonly used contraceptives do regularly kill an already formed infant by keeping it from attaching and remaining in the womb. The failure to keep fertilization from happening in the first place is common enough that every year at least twice as many** infants die due to contraceptive caused miscarrage at a very early date as do from abortions.
Let's look at some scientific facts here.
1) A fertilized ovum has a very small chance of surviving until implanting. It has, at most, a 25% chance of implanting. Even if it does implant, it still has about a 30% chance of dying. The woman will never know that an ovum was fertilized.
2) At the time of implantation, the fertilized ovum consists of fewer than 200 cells (actually, about 150). This is not enough cells to form any kind of structure. There are no organs, no nervous system, nothing to distinguish that clump of cells from any other clump of cells (and due to my background in medical research, I see a *lot* of clumps of cells). It does not have the physical capability of being aware of anything--it cannot know it's alive.
3) The nervous system begins to form at around 3 weeks post-fertilization. At that point, I'd say we have every obligation to protect that life, because it now has the physical ability to be aware and feel.
I won't conflate an embryo who has all of his/her organs and a functional nervous system with a fertilized egg. If that egg doesn't implant, pregnancy does not occur. I have no problem with that.
Thanks, good night.