I am happy to discuss the science and ethics of it with you if you take it seriously. jplowry is incredibly childish about such discussions and it's a waste of time going through it with him and there is no scientific merit to his responses.
Let's start with your point, which is really a semantic one: there are biochemical reactions within a fetus that chemically we call life, as indeed there are in a sperm cell or a tumor, both of which are genetically distinct from you. A sperm is technically a living thing. That cannot by any definition be the basis of life as needing legal protection, otherwise you'd be committing mass genocide every time you masturbate or cut off a cyst. Every time a woman has a period, an egg that could have been a baby dies and is flushed out: there is no way that that is somehow a murder, there's 40,000 of those things in a woman's body, she's not going to have 40,000 babies, that will never happen.
The fact is that doctors put much more weight on the growth, development, and relocation than you are giving credit for. The reason doctors cannot treat a fetus like it is already a person is because so many things are happening during a pregnancy that can go wrong. 10-20% of pregnancies will not be successful despite everyone's best efforts, and sometimes we never find out the reason. There is no reason to put couples through more heartbreak than they might already experience through sheer disappointment alone by telling them that it was a full human being that died in the womb. There's no medical reason why that's necessary. An acorn is not a tree, an egg is not a chicken, and we have actual children in the world to worry about.
For the purposes of medical life - not biochemical life in the technical sense that a gelatinous slime in a swamp might be considered to be living, but the medical sense of a human life - as well as the growth of all its organs, birth itself still involves the severing of the umbilical chord, the extraction from the amniotic sack, and the first breath of air - at which point, the baby gains consciousness and doctors can start treating it as though it is a tiny person. It is very common (e.g. Harman 1999) for doctors to state that medically, life begins at the gaining of what could be described as consciousness - and doctors themselves argue and scream at each other about this, but nobody can really come up with a good medical reason why this is not the case, and birth, for doctors, is the line.