I also don't want to discuss the traditional flame-war aspects of this! Apologies if I have. I'm happy to edit this post to avoid that intensely but shallowly interesting stuff.
In the UK there are moves to reduce the time limits for abortion. At the moment it is possible for a woman to have an abortion at under 24 weeks.
The science comes in because politicians say that it's possible for infants to survive if they're born under 24 weeks, and that's one reason to reduce the limits.
The problems are:
- we do not have abortion on demand in the UK. There can be delays in getting the tests and etc. This is one reason why abortions are sometimes carried out over 12 weeks. Changing the law to allow abortion on demand under 12 weeks may increase the numbers of those abortions, but also decrease the numbers of abortions carried out over 12 weeks.
- very few abortions are carried out at over 20 weeks. It's likely to be distressing for the woman and her partner. It's almost certainly because the child has a condition incompatible with life. This isn't just a child who will live a short and miserable life of a few years; it is a child who will live at most a few days. Reducing the time limits will increase the number of women forced to carry this child to term, and to give birth to it, and to watch it die after a few hours or days.
- Survivability of infants born under 24 weeks is not great. Doctors spend a lot of time (and money) making big interventions to keep these children alive. Many doctors and nurses do not feel that these interventions are humane.
You're right that most of the decisions to be made about abortion are purely moral, but some people are making scientificky claims for their position. Those people need to be using correct information.