This is an issue that is filled to the brim with arguments solely based in semantics. There are large issues in any discussion when the entire discussion is spent defining words, and arguing from those definitions. A common argument.
A fetus is just a sack of cells
Sacks of cells are fine to kill
A fetus is fine to kill
By such logic, it would also imply that anything else that could be considered a sack of cells is fine to kill, such as an adult human being. This is of course not the logical implication that many would approve of.
If a woman has a fetus and intends on delivering a baby, that if someone does something to kill the fetus against the woman's will, that the woman is entitled to take legal action for killing the fetus. If the woman did not intend on delivering the fetus, it is argued by pro-choice supporters that this is acceptable. The issue with such an argument is that it is really a claim that the mother's intention determines whether a fetus should have legal rights or not. This makes little sense as an intention cannot affect the property on an object.
To resolve this issue, it must first be argued that any abortion is really two acts. The fetus is aborted, and then it is killed. This is a key distinction because based on the eviction principle. The owner of a property has a right to evict a trespasser, but not to kill. A land owner would have the right to evict someone who came on their property, but not a right to outright kill them. Similarly, it can be well established that a women is the owner of her womb, and because of this the woman has the right to evict the fetus. But the woman does not have the right to kill the fetus. It is likely that evicting the fetus, especially at an early term will result in the death of a fetus, but this death is not the result of murder, but instead the result of the fetus being unable to survive outside the womb at such a time.
This shouldn't be taken as an argument to let aborted fetuses always die naturally, but more just illustrating the concept. It is completely rational to kill the fetus, or put it out of its misery, if it can be confirmed by qualified personal that the fetus is going to die.
To resolve the issue of intention, a woman who intends on having a baby has made an agreement to homestead that baby. This is similar to homesteading a pet. If you homestead a pet, it must be required that you take care of it and ensure healthy living conditions. If someone abuses the pet, it is the homesteader who is able to take legal action on the pet's behalf. A woman who intends on having a baby must currently be homesteading the fetus.
This gets rid of the issue of a current situation being predicated on a future intention. Intention is difficult to show, but active homesteading is not. For example, it can be reasoned that someone who does not feed their pets for a week has no intention of taking care of their pets in the future. It someone kills one of the pets to put it out of their misery, the man cannot take legal action on behalf of the dead pet because it is obvious that the man was not homesteading the pet, and any future claims to homesteading the pet would be considered baseless. In a similar way, a woman who intends on having a baby must also be performing actions that provide care to the fetus, such as eating, refraining from alcohol and other drugs, avoiding dangerous situations, and so on. It could not be reasoned that a woman who continued to smoke twenty packs a day, drove drunk at any chance, and starved themselves to death, would be taking any sort of action to homestead the baby. Though that example is extreme, any action that is not taken that is required to take care of a fetus would be proof of not having the intention of homesteading the fetus in the future.
Though, the above paragraph might seem a little random, it solves the legal issues involved in this sort of matter. Intention to homestead and actively homesteading are two completely different issues.
In conclusion, a woman has a right to evict, but not to kill.