In point 3's caveat, you mention the pain the fetus feels as a potential negative. There has to be a functioning nervous system for an organism to feel pain. For a long time in the development of the fetus, there just isn't enough of a nervous system to justify the thought that it feels pain. At some point in development, yes, of course. Regular charts of development usually peg 20 weeks as when the nervous system is starting to function. Most voluntary abortions take place well before that - well, they must as 12 weeks is the legal cut off. Abortions after that are usually only done to save the life of the mother or because the fetus is already non-viable or nearly so.

If we are talking about something like a chemical jump start to menstruation before or around the time of the first missed period, the blastocyst is not yet the size of a pen point and has only the most basic differentiation of cells called a "primitive streak" with the potential to develop into a spinal cord. There is certainly nothing there that could feel pain.

"By seven weeks, the embryo has lost its tail, which is another point of reference to our evolutionary ancestry. The higher functions of the brain have yet to develop, and there are no pathways to transfer pain signals. In fact, even at two months along, the embryo does not appear to be fully human. It has a reptilian brain and has not yet developed the capacity for consciousness. It is not yet sentient and is not defined as a fetus until the tenth week."

http://freethoughtblogs.com/alstefanelli/2011/10/17/abortion-is-not-murder/