Eh...
You wouldn't say it should be illegal for someone to refuse to give a body part to another person to save their life, right? You have to AGREE to give up a body part. You have to AGREE to donate blood. They can't just siphon your blood. They're not allowed to do it without your consent. It doesn't matter if it would save a life, it doesn't matter if you're the only person who could save that person. You have a choice.
An unborn child cannot be taken out of your body and survive. If it can, then it's obvious it shouldn't be aborted. Being pregnant is a selfless act, and requires you to give up your own body to birth a child. Your body is never going to go back to how it was previously. You're giving up your own body for life; it's beautiful and it's wonderful. Making that mandatory is horrible, and lacks empathy towards women who have ever gone through pregnancy or birth.
I don't understand how you can be anti-abortion but be in support of eugenics, though. If you view it as murder, then murdering the people you think "suffer beyond a reasonable point" is... well... I guess I don't want to get into it now. It just seems unusual is all.
Either way, people who talk about the life of the child AFTER it's already been born is missing the point. I don't have an interest in talking about whether or not a hypothetical child is going to live as a poor child or is going to become the smartest man on the planet. It has nothing to do with a made up child in a world full of billions of people; it's about the choice as someone who already exists and has a life, and whether or not that person is entitled to picking this specific medical procedure.
In my opinion, people should be allowed to seek medical treatment in general, for their own reasons, and I don't think they should need to justify it if it's not being billed through insurance. What would we ever gain by controlling someone else's body like that? Again, if the child is developed enough where it could survive outside of the body, then that's a different discussion in my opinion. Then it becomes about "when are they allowed to have an abortion?" rather than "should it be allowed at all?".