I’m very pro-choice, but I think your right that it’s not simple. The view that it’s simply the woman body is very simplistic and doesn’t stand up to much scrutiny - but it’s an effective top level view to guide your own beliefs to reach a conclusion.
It’s not universal, but I suspect that before conception the vast majority of people have no sentiment about the constituent cells. I find it difficult to hear that “life” begins at conception, as the cells were alive before conception - but i’ll take it as meaning belief of when a human is formed rather than life.
However, the human body naturally fails many pregnancies that are not viable at this point - so it’s not clear this is really significant. Additionally still after another 12 days or so the cells can split into twins, so the point of individual humans is ambiguous.
Equally, when does the baby acquire its own rights. It would seem very strange to believe most people would consider the baby that has just been born still attached to its mother is still part of the mother’s body - and five minutes earlier whilst still inside I doubt many would disagree there is no real difference.
So, there must be some point when the baby/foetus acquires it’s own rights - and the discussion is really when this is. So despite being pro-choice, the rights at conception argument could be a viable choice - but the logical conclusion of pro-choice, it’s the mothers choice until born is not viable imo. It is possible for a mother to die and the baby to survive, so the baby must be independent at that point.
It’s also not the case in society we don’t recognise parents have responsibilities. They have the responsibility to keep their children safe and to feed them - there is no reason to consider a embryo anything in another state of being fed and looked after - arguably it is not part of the mother’s body as the DNA in every cell is different.
I am not suggesting this, but a society could choose that the independent child inside the mother is the responsibility for the mother to keep safe, and any action that increases risk to the child is illegal - a society could choose that drinking whilst pregnant is illegal as a child protection issue.
We also consider someone dead when they cease brain activity. Although unpleasant, stabbing someone who has no brain activity is not murder. So, as a personal perspective I believe the point where the embryo acquires rights is similar - its when there is brain activity. Up to this point despite being a separate organism I don’t believe the embryo has consciousness, and whilst is “life” the human is not alive. After this point I believe the mother has a child and it is now her responsibility to look after the child.
I don’t know, but I suspect brain activity that we would call being “not dead” in later life is detected at around 25 weeks and this is the reason we limit abortion to 24 weeks. It could be better rather than choosing a timescale to simply see whether we can detect brain activity and use that, but I can understand the necessity of keeping it simple.
So all in all I think we’ve probably got it right - choice up to the point of consciousness and then responsibility rather than choice after consciousness. I would personally make it an absolute choice of the mother before consciousness - we essentially have it, but the right is cloaked.
The decision though is societies, not the individuals - and my rationale is just one voice in society. You may not agree, but if we can decide it’s valid to prohibit people from taking drugs and taking their own life - then there is nothing to suggest people have sole rights to control of their bodies in most societies.