A pregnant woman.
What characteristics define this noble creature? Hormonal, of course, and as it should be. Lacking in brain power, quite forgiveable, as the blood that normally visits there is now taken by a new life, which is such a beautiful thing that one can only smile when she forgets her phone number, where she left the car keys, and sometimes, her own name. Women who would never have this kind of problem under any other condition, any other stress...
In other words, a pregnant woman is the LAST person who should be making ANY sort of life changing decision, even in her OWN life.
Why, then, do we leave this decision up to her? It may be her body, but she is in an altered state during this time.
So why, how can we even think that this person should have a decision that could impact the world, and her own life, with such magnitude? It doesn't make any sense!
Alas, there is nobody that can choose for her, including herself. The woman, even before she is pregnant, is not properly equipped to choose. During the pregnancy, as discussed, is not fit to choose. After the pregnancy is too late. It is nobody else's right to make the decision for her. I can think of only one other soul who has any right to choose in this instance - and they are not born yet, not nearly old enough to choose.