A foetus is not a human being. The rights of human beings already born (the mother and any existing children) are more important.
Here are some of the (non-medical) reasons women abort towards the 24 week limit now- www.bpas.org/media/2027/late-abortion-report-v02.pdf
and www.bpas.org/media/1202/second_trimester_abortions__ingham.pdf
When we are talking about later term abortions, it's really important to remember we are talking about a very small number of women often in difficult and desperate situations- only 1-2% of all abortions.
A significant proportion of these women will not know they are pregnant before 12-14 weeks, they have not shown typical symptoms and are still bleeding or do not have regular periods. They may well be using contraception that affects their period as well. They haven't been pregnant for 20 weeks and known about it for 10 and suddenly gone "Oh actually I want an abortion". They've found out at maybe 20 weeks and are having to deal with the situation. It must be horrible for them and they deserve our compassion, not our judgement. Sometimes, these are young girls, rather than grown women. Making them carry a baby to term that they don't want and can't look after would be incredibly psychologically damaging.
The other sort of woman seeking later term abortion have often had a sudden circumstance change such as becoming homeless, or their partner has become violent, or they've had some other type of financial problem. They may already have children. Having to carry a pregnancy to term in these circumstances makes everything more challenging and difficult, especially as they have decided they can't look after the child when it is born.
Why is it ok for a woman to say at any stage they couldn't cope with a disabled child, but not with a healthy one when they may be in very difficult circumstances?
From a societal point of view, we are an overcrowded planet- encouraging women to have more children is not a good thing, long term. Having more unwanted children (especially if born early) is not something we as a society actually want or need. Those who are totally anti-abortion on this thread, I hope you have adopted a relinquished child, or done something to support mothers in difficult circumstances- otherwise you are just passing that burden on to everyone.
As early as possible, as late as necessary, all children born loved and wanted.