Medically-speaking, fetus can't "take" anything in context of a process that's designed to do what it's supposed to do - produce a child.
A car doesn't "take" tires from a factory. Factory is producing a car as a process.
Likewise, it's a symbiotic process in context of societal dynamics. We take care of our children, and our children then take care of us. That's how humanity was able to achieve what we have today.
What you wrote is that:
1) It's a "hostage situation", which is absurd. We have a very specific definition for hostage situation, and it's generally involves HOSTILITY, or from latin hostis - a stranger or enemy. Just because host and hostage share first 4 letters doesn't make them semantically same.
2) Sure, parent is much more than a caregiver, we agree. Yes, virtually all of the parents are taking on these responsibilities to their detriment, both physically, financially, psychologically, you name it.
BUT
The comfort that you are experiencing today when it comes to having a society of people that built stuff that works is predominately because there are parents who don't abdicate their parental responsibilities to keep societies functional.
I know it's difficult to grasp having the atomized view of "my body... I can do what I want", but your body wouldn't exist if your parents didn't choose to go through the trouble of feeding you through maturity. Just because we have a right to bodily integrity (no forceful organ removal or blood donation), don't mean that we all of a sudden don't have responsibilities as parents or as a members of a society which has a long history of people trying to provide viable means of existence for other people. If we collectively care about disabled and unwanted children, I think we should collectively care about unwanted "fetuses".