By way of illustration:
No person can be legally required to donate blood or part of their body. Even in the most ludicrous example you could think of: a drunk driver mortally injures someone and could save their life by donating blood. Even though the situation is their fault, isn't legally compelled to give blood. Those are extreme examples, and hundreds more that are far less intense exist. In none of them is a person required to surrender their bodily autonomy.
A fetus has no right to require the use of a woman's body for nine months of she doesn't want to. Even if she fucks 80 men a day without protection, who gets to use her uterus to gestate in is exclusively her decision.
Counterpoint. How about a conjoined twin who attempts suicide by overdose. Irrespective of your views on suicide should this be allowed?
That's a pretty interesting question with a lot of pieces to pick apart. If I wasn't really fucking tired from working all week I might be able to engage it properly.