There’s no analogy that could come close to approximating fertilizing an egg and then removing it from the environment necessary for it to continue living. The argument is not about whether or not killing this living thing is immoral or not, it’s about our ability to decide when the living thing has the opportunity to think and feel and experience life.
It’s certainly not without a brain to process stimuli, and sometimes even still after having the required parts for life outside the womb, the fetus miscarries, or has the potential to kill its mother. I think there’s a word for when we decide that the human changes from fetus to baby when it’s first day outside of the womb is, hmmm? And even still after that day that it’s “born” it might still not be able to live for long. What pro-choice people are attempting to say is that there’s no indicator of any sort of the ability of a pregnancy to carry to term until it comes out of the mother and lives to remember what it does, so it doesn’t make sense to write away the mortality of ending it before we know if it’s gonna be a baby by declaring it already is one. Not only does the complete ban of abortion sentence mothers that need it in medical emergency to death, but it doesn’t solve the issue of people getting abortions. Is it illegal to murder someone with a firearm? THEN WHY THE FUCK DO WE KEEP KILLING SO MANY PEOPLE