People on the pro side often frame it as purely a women's rights or an autonomy issue. But opponents of abortion are usually concerned with something much bigger. Imagine if fetuses were so developed after a couple months that you could talk them and they were going "Please don't let mommy abort me" - would you let abortion happen anyway because 'her body, her rules'? Or tell the baby that it's the product of rape, and we can't reasonably expect your mother to deal with that, so down the toilet you go? The real source of the disagreement is usually whether or not abortion is murdering a Person, which is unjustifiable, or discarding a clump of valueless cells, which anyone should be able to do on a whim, or something inbetween. Those on one extreme end who think a fetus is as valuable as an adult will never accept abortion, and those who think a fetus has no value at all will push against all restrictions.
So we have to decide what exactly makes a person a person. There's some special quality that you and I have that makes it a moral negative to cause harm to us, but something that nobody cares about like an ant has none of this special quality, whatever it is. Is it consciousness, awareness, intelligence, being biologically human, having a 'soul', or some mix of those? This is a philosophical question, there's no provable right or wrong, everyone has their own answer. But whatever that answer is, I think it must be a single consistent one. If you change your reasoning in every situation so that it matches your gut feeling, then you have no reasoning at all. So we can poke at each other's answers with thought experiments.
For example - if you don't think brain dead adults and babies with anencephaly have to be cared for, I think you should be willing to abort a fetus without brain activity.
And is the mere presence of brain activity enough? Is that the distinction that makes a fetus worth protecting? If so, should every organism with a working brain get similar protection?
And to go even further, suppose like most people you're not overly concerned with animal shelters euthanizing dogs nobody wants to care for, because dogs just aren't that smart. Then what's your opinion about humans that are dumber than dogs?
That's the road my reasoning goes down. The most defensible conclusion I've got is to say that life should be valued based on its position on some vague scale of consciousness and intelligence, as best as we can measure those things. Since I don't think babies in the womb fall anywhere on that scale that I'm remotely worried about, women can buy an abortion kit over the counter at 8.5 months for all I care. But if someone else stops at step 1 and says that any living human is sacred, or if they say that a 3rd trimester fetus in their opinion has enough mental development to deserve some rights, those can be reasoned and consistent positions too.