Foetuses do not have an ‘instinctive will to live’. I have had three miscarriages and my sister had a stillbirth at term. I think the statistic is 1 in 4 pregnancies end in miscarriage. Thankfully stillbirths are much, much rarer. But to say that foetuses and babies have ‘an instinctive will to live’ is fairly tone deaf to anyone who has experienced foetal or neonatal loss.
The last paragraph of your argument brings in people with severe mental incapacity or children under three, but the point about abortion limits is about when the foetus becomes a legal entity, not people who have already drawn breath. If we are talking about people who have already drawn breath, we are into the realms of eugenics, not feminism. Of course abortion advocacy earlier in the twentieth century was linked with eugenics as was the birth control movement, which is one reason I always think it is important to remember that choice has two sides - the right to give birth as well as not, and that the more support is taken away from pregnant women and the more pressure to have an abortion as their circumstances are not ‘right’ or there is something wrong with the foetus, the more that choice is eroded - in other words, the more that wider societal and economic pressures, even community and family pressures impinge on that choice, the less it is actually a choice. (Here, I would also include the lack of appropriate facilities for disability care and support for parents of disabled children).
The slogan, my body, my choice, tries to strip away all these complex social, economic, medical, community and family pressures and centres the woman who has to either carry the baby and birth the baby and her reproductive autonomy. The slogan trusts her to be the best judge of her social and economic circumstances, medical situation, community and family pressures and make the informed choice of what is best to do. This is a feminist position, in my opinion.
And whilst it may sound extremist to say that this also includes abortion near term, in fact, as many, many posters have pointed out on this thread, the vast, vast majority of abortions are in the early weeks. It is also more difficult to access later abortion. If a woman is inducing abortion after the legal limit, and without there being medical reasons for this, she is likely doing it alone and without appropriate care. Then the question becomes what has gone wrong? Why has a woman got to the position she is so desperate that it seems better to risk an illicit abortion or rather, bring about a stillbirth, than carry this baby to term and birth this baby? That she has got to this position is an indictment of society and the messages and support society gives to mothers and women who are pregnant.
In such a situation, the question ‘are you are feminist to support this?’ actually means ‘do you support the woman in this position and extend understanding, compassion and care, or do you think she should be prosecuted?’.