This is a bit disingenuous. "A fetus is a person and the state should force it to be carried to term" is generally not the argument, the argument is "A fetus is a person and you should not be allowed to actively kill it."
Alternatively, say you donated blood, and that blood is used to keep someone alive. Then they run out of that blood and need more, and you are the only option, but you've developed anemia or something, so no longer want to donate blood, by your own definition the state can now require you to keep giving blood anyway: This person is only alive now because of your actions, and your attempt to change those conditions would kill them.
Also the policy is "you should be forced to carry it to term", because abortion bans also come with a variety of bans on access to emergency contraceptives that would prevent it from even getting to the point of being a fetus in the first place, and the women-aren't-people crowd fight anything and everything else that would prevent many abortions occurring in the first place (access to contraceptives, actual sex ed, etc)