I guess I do it in the same way as the fact that none of us, as organisms, has an independent life. The oxygen I breathe is produced by plants and the CO2 I exhale is taken in by plants. I eat things. They eat other things or grow based on energy from the sun.
In this case the foetus is dependent mostly on one other organism, the pregnant woman. But I don't see a moral line between dependence on one organism and dependance on many.
I never said the woman should put their own needs and wishes last. They are an important factor, but not the only factor IMHO. It is unacceptable to euthanise a born child because they are detrimental to the mental, physical or financial health of their mother, siblings etc. I agree it is more acceptable to euthanise an unborn child than a born one, particularly in the early stages of gestation where capacity for thought and feeling pain are not yet developed. But I don't think it is acceptable in its own right. Only when held in balance with the needs of the other parties involved - usually the pregnant woman. And that argument could also be made for a born child - if they were a huge drain financially, emotionally, physically, in all ways possible then why would it be wrong to decide the family's needs are more important than the young baby's needs and that overall the right answer is to euthanise the child? I struggle to see a moral difference. Practical difference, yes. Tipping the balance due to the reduced ability of a foetus to feel, think, act, express wishes, and the reduced probability of reaching healthy adulthood, yes. But all these arguments are just saying the foetus's benefit is less weighty than the born child's benefit, not that they don't exist at all.
I'm not saying abortion should be banned or anything like that. The woman's needs ARE important. But just as the woman's needs should not ALWAYS be last, they should also not ALWAYS be first. Perhaps they should have more weight than the needs of the foetus because she is more sentient, more likely to survive to adulthood, dependent on a higher number of other organisms rather than just one. But the foetus's needs should be on the list too. I think the woman is actually the best placed to do this weighing. But she is also a biased party to that decision.
I think its a genuinely thorny moral dilemma, and not at all as clear cut as "my body my choice" (the foetus also has a body) or "anyone who is against abortion is deliberately supressing women in general" (anyone who is for it is deliberately supressing foetusses?).
I am really grateful for this thread though for exposing me to other's points of view and giving me food for thought - it has made me question my opinion and change it in some regards.