Embryos and fetus ARE NOT parasites. They might share traits, but then, so do infants and toddlers vis-a-vis the household.
But having a mind is a good point. If we look at the other end of life, it’s the criteria that’s used all the time to decide whether to keep someone on life support or not. When people are in a persistent vegetative state; when their brains, for whatever reason - disease, trauma - has been heavily damaged, decisions are made to end those lives based mostly on that criteria. They are just as emotional and difficult to make too.
If the fetus, higher brain functions appear between the 20th and 27th week. Aborting a fetus in the first trimester is still a hard decision (at least, it should be) and an emotional one, but there can be no awareness from the fetus, no more than there would be from unplugging a motorcycle crash victim who’s helmet saved his life but not his mind.
Last point: It’d be more honest from the “pro-life” side (as if anyone is “anti-life”) to stop arguing as if all abortions are late third trimester ones. Close to 95% of abortions occur before the 12th week, when the fetus is still well in the “Republican” stage. Most “pro-choice” (again, as if anyone is “anti-choice…” are those labels chosen to enflame already emotional debates?) people I know are against 3rd trimester abortions. Even Canada’s famed (or infamous, depending on your views) Dr. Henry Morgentaler has repeatedly said that he’s ethically opposed to aborting a fetus passed the 24th week.
So it basically comes down to when you believe “personhood” starts. Not when “life” starts. Life started 4 billion years ago and hasn’t been interrupted since. The ovum and spermatozoa are just as alive as you are, and as the fecunded egg is. Same goes for the zygote, embryo, fetus… it’s all alive. But sperm, ovums, zygotes, embryos, etc. aren’t “persons.” They have no mind.
If you believe life to begin at conception, then you must accept the fact that something like 60% of all lives never make it. Many embryos never implant in the womb, for various reasons. And many of those that do implant will still be washed away. Most evacuations occur on the natural menstrual cycle so the woman never even knows she was pregnant for a short time… some occur later (miscarriages). Nature (or God, if you believe), it seems, considers life to be rather cheap and disposable.
If you believe that “personhood” occurs at birth, then you’re a bit late. Millions of premature babies will attest to the fact that the baby was entirely viable even if they where born at 27, 28 or 32 weeks. Recently, babies born at 24 or 25 weeks have been “saved” but all of them (at least, I’m not aware of a single exception) suffer from mental retardation at various degrees, tending toward the heavily challenged side.
It basically comes down to a value judgment. Personally, while I wish that no abortions ever had to be performed; that people would use birth control and act responsibly, think that first trimester abortions are better than the alternative double whammy of illegal backstreet abortions with a bunch of unwanted kids thrust into the world. I’m not too comfortable with later abortions. 2nd trimester, I’d support if there is a medical condition that warrants it (ie, the life of the mother is in danger). 3rd trimester is out. The fetus is viable at that point, tough it out or get a C-section and give it up for adoption.