Matters not, biology says the child is equally his, science, you know biology, and creation, and more of those sciency words you do not like, are the reason she carries the child!
"If my younger sister was in a car accident and desperately needed a blood transfusion to live, and I was the only person on Earth who could donate blood to save her, and even though donating blood is relatively easy, safe, and quick procedure, NO ONE CAN FORCE ME TO GIVE BLOOD. Yes, even to save the life of a fully grown person, it would be ILLEGAL and UNETHICAL to force me to donate blood if I didn't want to.
See, we have this concept called "bodily autonomy". It's this cultural notion that a person's control over their own body is above all important and must not be infringed upon.
We can't even take LIFE SAVING ORGANS from corpses unless the person whose corpse it is gave consent before their death. Even dead bodies get bodily autonomy.
To tell people that they must sacrifice their bodily autonomy for 9 months against their will in an incredibly expensive, invasive, difficult process to save what YOU view as another human life (a debatable claim in the early stages of pregnancy when the vast majority of abortions are performed) is
deeply, desperately, depravedly unethical. You can't even ask people to sacrifice bodily autonomy to give up organs they aren't using anymore after they have died.
You're demanding women accept less bodily autonomy than you give to dead bodies."
And furthermore, if you demand that women must carry a pregnancy to full term, then you must also support the state pulling organs out of your body (dead or alive) to save the life of someone else...someone you don't know, have never met, and will never meet.