Okay, first off, making abortions illegal means that abortions will be performed haphazardly and dangerously. The legalization of abortion was more a case of legalizing the status quo than anything else. It's an ineffective measure because it doesn't do anything to address the issues that lead to a mother choosing to have an abortion.
Now, you may be fine with drawing your particular line at "egg cell has been fertilized and is implanted". I'm not, and I'm not going to get into specifics any further than this post. My reasoning is that, as soon as the foetus is developed enough that it can be transferred into a mechanical womb, then that procedure should be used (assuming, of course, that the state foots the bill for the procedure, the high-intensity med care that follows, and the eventual adoption). As I said, this preserves the rights of the unborn and the mother simultaneously. Before that point, all I can say is that I value the rights of an actual person higher than those of a person in potentia. I can try to rationalize this, but at its core, it's an emotional decision.
Ultimately though, I do not have the right to tell another person what he or she may do with her body. I may assist in making a decision, but it is ultimately not mine to make, and once a decision has been reached, it is my responsibility to help deal with the consequences if required. Based on that, I cannot support any attempt to reduce another's bodily autonomy through force of law.